Para hallar los extremos hay que resolver la ecuación
$$\frac{d}{d x} f{\left(x \right)} = 0$$
(la derivada es igual a cero),
y las raíces de esta ecuación serán los extremos de esta función:
$$\frac{d}{d x} f{\left(x \right)} = $$
primera derivada$$\frac{4 x^{3}}{- 2 x^{4} + 3 x} + \frac{\left(8 x^{3} - 3\right) \left(x^{4} + 8\right)}{\left(- 2 x^{4} + 3 x\right)^{2}} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = - \frac{16}{9} - \frac{\sqrt{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + \frac{2048}{81} + \frac{65536}{729 \sqrt{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}}}}{2}$$
$$x_{2} = - \frac{\sqrt{- 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + \frac{2048}{81} + \frac{65536}{729 \sqrt{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}}}}{2} - \frac{16}{9} - \frac{\sqrt{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}}{2}$$
Signos de extremos en los puntos:
4
/ _________________________________________________________________________________________________________________________________________________________________ \
| / _______________________ |
_________________________________________________________________________________________________________________________________________________________________ | / / _______ |
/ _______________________ | / 2048 / 2048 16*\/ 16546 16 65536 |
/ / _______ | / ---- - 2*3 / - ---- + ------------ + ------------------------------ + -------------------------------------------------------------------------------------- |
/ 2048 / 2048 16*\/ 16546 16 65536 | / 81 \/ 243 243 _______________________ ________________________________________________________________________ ________________________________________________________________________|
/ ---- - 2*3 / - ---- + ------------ + ------------------------------ + -------------------------------------------------------------------------------------- | / / _______ / _______________________ / _______________________ |
/ 81 \/ 243 243 _______________________ ________________________________________________________________________ ________________________________________________________________________ | / / 2048 16*\/ 16546 / / _______ / / _______ |
/ / _______ / _______________________ / _______________________ | / 9*3 / - ---- + ------------ / 1024 / 2048 16*\/ 16546 16 / 1024 / 2048 16*\/ 16546 16 |
/ / 2048 16*\/ 16546 / / _______ / / _______ | / \/ 243 243 729* / ---- + 2*3 / - ---- + ------------ - ------------------------------ / ---- + 2*3 / - ---- + ------------ - ------------------------------ |
/ 9*3 / - ---- + ------------ / 1024 / 2048 16*\/ 16546 16 / 1024 / 2048 16*\/ 16546 16 | / / 81 \/ 243 243 _______________________ / 81 \/ 243 243 _______________________ |
/ \/ 243 243 729* / ---- + 2*3 / - ---- + ------------ - ------------------------------ / ---- + 2*3 / - ---- + ------------ - ------------------------------ | / / / _______ / / _______ |
/ / 81 \/ 243 243 _______________________ / 81 \/ 243 243 _______________________ | / / / 2048 16*\/ 16546 / / 2048 16*\/ 16546 |
/ / / _______ / / _______ | / / 9*3 / - ---- + ------------ / 9*3 / - ---- + ------------ |
/ / / 2048 16*\/ 16546 / / 2048 16*\/ 16546 | 16 \/ \/ \/ 243 243 \/ \/ 243 243 |
/ / 9*3 / - ---- + ------------ / 9*3 / - ---- + ------------ 8 + |- -- + -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- - ----------------------------------------------------------------------------------|
16 \/ \/ \/ 243 243 \/ \/ 243 243 \ 9 2 2 /
(- -- + -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- - ----------------------------------------------------------------------------------, --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------)
9 2 2 4
/ _________________________________________________________________________________________________________________________________________________________________ \ _________________________________________________________________________________________________________________________________________________________________
| / _______________________ | / _______________________
| / / _______ | / / _______
| / 2048 / 2048 16*\/ 16546 16 65536 | / 2048 / 2048 16*\/ 16546 16 65536
| / ---- - 2*3 / - ---- + ------------ + ------------------------------ + -------------------------------------------------------------------------------------- | 3* / ---- - 2*3 / - ---- + ------------ + ------------------------------ + --------------------------------------------------------------------------------------
| / 81 \/ 243 243 _______________________ ________________________________________________________________________ ________________________________________________________________________| ________________________________________________________________________ / 81 \/ 243 243 _______________________ ________________________________________________________________________
| / / _______ / _______________________ / _______________________ | / _______________________ / / _______ / _______________________
| / / 2048 16*\/ 16546 / / _______ / / _______ | / / _______ / / 2048 16*\/ 16546 / / _______
| / 9*3 / - ---- + ------------ / 1024 / 2048 16*\/ 16546 16 / 1024 / 2048 16*\/ 16546 16 | / 1024 / 2048 16*\/ 16546 16 / 9*3 / - ---- + ------------ / 1024 / 2048 16*\/ 16546 16
| / \/ 243 243 729* / ---- + 2*3 / - ---- + ------------ - ------------------------------ / ---- + 2*3 / - ---- + ------------ - ------------------------------ | 3* / ---- + 2*3 / - ---- + ------------ - ------------------------------ / \/ 243 243 729* / ---- + 2*3 / - ---- + ------------ - ------------------------------
| / / 81 \/ 243 243 _______________________ / 81 \/ 243 243 _______________________ | / 81 \/ 243 243 _______________________ / / 81 \/ 243 243 _______________________
| / / / _______ / / _______ | / / _______ / / / _______
| / / / 2048 16*\/ 16546 / / 2048 16*\/ 16546 | / / 2048 16*\/ 16546 / / / 2048 16*\/ 16546
| / / 9*3 / - ---- + ------------ / 9*3 / - ---- + ------------ | / 9*3 / - ---- + ------------ / / 9*3 / - ---- + ------------
16 | 16 \/ \/ \/ 243 243 \/ \/ 243 243 | \/ \/ 243 243 \/ \/ \/ 243 243
- -- - 2*|- -- + -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- - ----------------------------------------------------------------------------------| - ------------------------------------------------------------------------------------ + ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
3 \ 9 2 2 / 2 2
4
/ _________________________________________________________________________________________________________________________________________________________________\
| / _______________________ |
_________________________________________________________________________________________________________________________________________________________________ | / / _______ |
/ _______________________ | / 2048 / 2048 16*\/ 16546 16 65536 |
/ / _______ | / ---- - 2*3 / - ---- + ------------ + ------------------------------ + -------------------------------------------------------------------------------------- |
/ 2048 / 2048 16*\/ 16546 16 65536 | ________________________________________________________________________ / 81 \/ 243 243 _______________________ ________________________________________________________________________ |
/ ---- - 2*3 / - ---- + ------------ + ------------------------------ + -------------------------------------------------------------------------------------- | / _______________________ / / _______ / _______________________ |
________________________________________________________________________ / 81 \/ 243 243 _______________________ ________________________________________________________________________ | / / _______ / / 2048 16*\/ 16546 / / _______ |
/ _______________________ / / _______ / _______________________ | / 1024 / 2048 16*\/ 16546 16 / 9*3 / - ---- + ------------ / 1024 / 2048 16*\/ 16546 16 |
/ / _______ / / 2048 16*\/ 16546 / / _______ | / ---- + 2*3 / - ---- + ------------ - ------------------------------ / \/ 243 243 729* / ---- + 2*3 / - ---- + ------------ - ------------------------------ |
/ 1024 / 2048 16*\/ 16546 16 / 9*3 / - ---- + ------------ / 1024 / 2048 16*\/ 16546 16 | / 81 \/ 243 243 _______________________ / / 81 \/ 243 243 _______________________ |
/ ---- + 2*3 / - ---- + ------------ - ------------------------------ / \/ 243 243 729* / ---- + 2*3 / - ---- + ------------ - ------------------------------ | / / _______ / / / _______ |
/ 81 \/ 243 243 _______________________ / / 81 \/ 243 243 _______________________ | / / 2048 16*\/ 16546 / / / 2048 16*\/ 16546 |
/ / _______ / / / _______ | / 9*3 / - ---- + ------------ / / 9*3 / - ---- + ------------ |
/ / 2048 16*\/ 16546 / / / 2048 16*\/ 16546 | 16 \/ \/ 243 243 \/ \/ \/ 243 243 |
/ 9*3 / - ---- + ------------ / / 9*3 / - ---- + ------------ 8 + |- -- - ---------------------------------------------------------------------------------- - --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
16 \/ \/ 243 243 \/ \/ \/ 243 243 \ 9 2 2 /
(- -- - ---------------------------------------------------------------------------------- - --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------, --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------)
9 2 2 4
/ _________________________________________________________________________________________________________________________________________________________________\ _________________________________________________________________________________________________________________________________________________________________
| / _______________________ | / _______________________
| / / _______ | / / _______
| / 2048 / 2048 16*\/ 16546 16 65536 | / 2048 / 2048 16*\/ 16546 16 65536
| / ---- - 2*3 / - ---- + ------------ + ------------------------------ + -------------------------------------------------------------------------------------- | 3* / ---- - 2*3 / - ---- + ------------ + ------------------------------ + --------------------------------------------------------------------------------------
| ________________________________________________________________________ / 81 \/ 243 243 _______________________ ________________________________________________________________________ | ________________________________________________________________________ / 81 \/ 243 243 _______________________ ________________________________________________________________________
| / _______________________ / / _______ / _______________________ | / _______________________ / / _______ / _______________________
| / / _______ / / 2048 16*\/ 16546 / / _______ | / / _______ / / 2048 16*\/ 16546 / / _______
| / 1024 / 2048 16*\/ 16546 16 / 9*3 / - ---- + ------------ / 1024 / 2048 16*\/ 16546 16 | / 1024 / 2048 16*\/ 16546 16 / 9*3 / - ---- + ------------ / 1024 / 2048 16*\/ 16546 16
| / ---- + 2*3 / - ---- + ------------ - ------------------------------ / \/ 243 243 729* / ---- + 2*3 / - ---- + ------------ - ------------------------------ | 3* / ---- + 2*3 / - ---- + ------------ - ------------------------------ / \/ 243 243 729* / ---- + 2*3 / - ---- + ------------ - ------------------------------
| / 81 \/ 243 243 _______________________ / / 81 \/ 243 243 _______________________ | / 81 \/ 243 243 _______________________ / / 81 \/ 243 243 _______________________
| / / _______ / / / _______ | / / _______ / / / _______
| / / 2048 16*\/ 16546 / / / 2048 16*\/ 16546 | / / 2048 16*\/ 16546 / / / 2048 16*\/ 16546
| / 9*3 / - ---- + ------------ / / 9*3 / - ---- + ------------ | / 9*3 / - ---- + ------------ / / 9*3 / - ---- + ------------
16 | 16 \/ \/ 243 243 \/ \/ \/ 243 243 | \/ \/ 243 243 \/ \/ \/ 243 243
- -- - 2*|- -- - ---------------------------------------------------------------------------------- - --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| - ------------------------------------------------------------------------------------ - ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
3 \ 9 2 2 / 2 2
Intervalos de crecimiento y decrecimiento de la función:Hallemos los intervalos donde la función crece y decrece y también los puntos mínimos y máximos de la función, para lo cual miramos cómo se comporta la función en los extremos con desviación mínima del extremo:
Puntos mínimos de la función:
$$x_{1} = - \frac{16}{9} - \frac{\sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + \frac{2048}{81} + \frac{65536}{729 \sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}}}{2}$$
Puntos máximos de la función:
$$x_{1} = - \frac{\sqrt{- 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + \frac{2048}{81} + \frac{65536}{729 \sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}}}{2} - \frac{16}{9} - \frac{\sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}{2}$$
Decrece en los intervalos
$$\left(-\infty, - \frac{\sqrt{- 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + \frac{2048}{81} + \frac{65536}{729 \sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}}}{2} - \frac{16}{9} - \frac{\sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}{2}\right] \cup \left[- \frac{16}{9} - \frac{\sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + \frac{2048}{81} + \frac{65536}{729 \sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}}}{2}, \infty\right)$$
Crece en los intervalos
$$\left[- \frac{\sqrt{- 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + \frac{2048}{81} + \frac{65536}{729 \sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}}}{2} - \frac{16}{9} - \frac{\sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}{2}, - \frac{16}{9} - \frac{\sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + \frac{2048}{81} + \frac{65536}{729 \sqrt{\left|{- \frac{16}{9 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}}} + 2 \sqrt[3]{- \frac{2048}{243} + \frac{16 \sqrt{16546}}{243}} + \frac{1024}{81}}\right|}}}}{2}\right]$$