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$$45 x^{4} + 12 x^{3} - 7 = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = - \frac{1}{15} - \frac{\sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}} + \frac{8}{225} + \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{16}{3375 \sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}}}{2}$$
$$x_{2} = - \frac{\sqrt{- 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}} + \frac{8}{225} + \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{16}{3375 \sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}}}{2} - \frac{1}{15} - \frac{\sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}{2}$$
Signos de extremos en los puntos:
4 5
________________________________________________________________________________________________________________________________________________________________ / ________________________________________________________________________________________________________________________________________________________________ \ / ________________________________________________________________________________________________________________________________________________________________ \ ________________________________________________________________________________________________________________________________________________________________
/ ______________________ | / ______________________ | | / ______________________ | / ______________________
/ / ______ | / / ______ | | / / ______ | / / ______
/ 8 / 7 7*\/ 2634 14 16 | / 8 / 7 7*\/ 2634 14 16 | | / 8 / 7 7*\/ 2634 14 16 | / 8 / 7 7*\/ 2634 14 16
/ --- - 2*3 / - ----- + ---------- + ------------------------------- + -------------------------------------------------------------------------------------- | / --- - 2*3 / - ----- + ---------- + ------------------------------- + -------------------------------------------------------------------------------------- | | / --- - 2*3 / - ----- + ---------- + ------------------------------- + -------------------------------------------------------------------------------------- | 7* / --- - 2*3 / - ----- + ---------- + ------------------------------- + --------------------------------------------------------------------------------------
/ 225 \/ 10125 30375 ______________________ _______________________________________________________________________ _______________________________________________________________________ | / 225 \/ 10125 30375 ______________________ _______________________________________________________________________ _______________________________________________________________________| | / 225 \/ 10125 30375 ______________________ _______________________________________________________________________ _______________________________________________________________________| / 225 \/ 10125 30375 ______________________ _______________________________________________________________________ _______________________________________________________________________
/ / ______ / ______________________ / ______________________ | / / ______ / ______________________ / ______________________ | | / / ______ / ______________________ / ______________________ | / / ______ / ______________________ / ______________________
/ / 7 7*\/ 2634 / / ______ / / ______ | / / 7 7*\/ 2634 / / ______ / / ______ | | / / 7 7*\/ 2634 / / ______ / / ______ | / / 7 7*\/ 2634 / / ______ / / ______
/ 135*3 / - ----- + ---------- / 4 / 7 7*\/ 2634 14 / 4 / 7 7*\/ 2634 14 | / 135*3 / - ----- + ---------- / 4 / 7 7*\/ 2634 14 / 4 / 7 7*\/ 2634 14 | | / 135*3 / - ----- + ---------- / 4 / 7 7*\/ 2634 14 / 4 / 7 7*\/ 2634 14 | / 135*3 / - ----- + ---------- / 4 / 7 7*\/ 2634 14 / 4 / 7 7*\/ 2634 14
/ \/ 10125 30375 3375* / --- + 2*3 / - ----- + ---------- - ------------------------------- / --- + 2*3 / - ----- + ---------- - ------------------------------- | / \/ 10125 30375 3375* / --- + 2*3 / - ----- + ---------- - ------------------------------- / --- + 2*3 / - ----- + ---------- - ------------------------------- | | / \/ 10125 30375 3375* / --- + 2*3 / - ----- + ---------- - ------------------------------- / --- + 2*3 / - ----- + ---------- - ------------------------------- | / \/ 10125 30375 3375* / --- + 2*3 / - ----- + ---------- - ------------------------------- 7* / --- + 2*3 / - ----- + ---------- - -------------------------------
/ / 225 \/ 10125 30375 ______________________ / 225 \/ 10125 30375 ______________________ | / / 225 \/ 10125 30375 ______________________ / 225 \/ 10125 30375 ______________________ | | / / 225 \/ 10125 30375 ______________________ / 225 \/ 10125 30375 ______________________ | / / 225 \/ 10125 30375 ______________________ / 225 \/ 10125 30375 ______________________
/ / / ______ / / ______ | / / / ______ / / ______ | | / / / ______ / / ______ | / / / ______ / / ______
/ / / 7 7*\/ 2634 / / 7 7*\/ 2634 | / / / 7 7*\/ 2634 / / 7 7*\/ 2634 | | / / / 7 7*\/ 2634 / / 7 7*\/ 2634 | / / / 7 7*\/ 2634 / / 7 7*\/ 2634
/ / 135*3 / - ----- + ---------- / 135*3 / - ----- + ---------- | / / 135*3 / - ----- + ---------- / 135*3 / - ----- + ---------- | | / / 135*3 / - ----- + ---------- / 135*3 / - ----- + ---------- | / / 135*3 / - ----- + ---------- / 135*3 / - ----- + ----------
1 \/ \/ \/ 10125 30375 \/ \/ 10125 30375 37 | 1 \/ \/ \/ 10125 30375 \/ \/ 10125 30375 | | 1 \/ \/ \/ 10125 30375 \/ \/ 10125 30375 | \/ \/ \/ 10125 30375 \/ \/ 10125 30375
(- -- + ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- - ---------------------------------------------------------------------------------, -- + 3*|- -- + ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- - ---------------------------------------------------------------------------------| + 9*|- -- + ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- - ---------------------------------------------------------------------------------| - --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- + -----------------------------------------------------------------------------------)
15 2 2 15 \ 15 2 2 / \ 15 2 2 / 2 2
4 5
________________________________________________________________________________________________________________________________________________________________ / ________________________________________________________________________________________________________________________________________________________________\ / ________________________________________________________________________________________________________________________________________________________________\ ________________________________________________________________________________________________________________________________________________________________
/ ______________________ | / ______________________ | | / ______________________ | / ______________________
/ / ______ | / / ______ | | / / ______ | / / ______
/ 8 / 7 7*\/ 2634 14 16 | / 8 / 7 7*\/ 2634 14 16 | | / 8 / 7 7*\/ 2634 14 16 | / 8 / 7 7*\/ 2634 14 16
/ --- - 2*3 / - ----- + ---------- + ------------------------------- + -------------------------------------------------------------------------------------- | / --- - 2*3 / - ----- + ---------- + ------------------------------- + -------------------------------------------------------------------------------------- | | / --- - 2*3 / - ----- + ---------- + ------------------------------- + -------------------------------------------------------------------------------------- | 7* / --- - 2*3 / - ----- + ---------- + ------------------------------- + --------------------------------------------------------------------------------------
_______________________________________________________________________ / 225 \/ 10125 30375 ______________________ _______________________________________________________________________ | _______________________________________________________________________ / 225 \/ 10125 30375 ______________________ _______________________________________________________________________ | | _______________________________________________________________________ / 225 \/ 10125 30375 ______________________ _______________________________________________________________________ | _______________________________________________________________________ / 225 \/ 10125 30375 ______________________ _______________________________________________________________________
/ ______________________ / / ______ / ______________________ | / ______________________ / / ______ / ______________________ | | / ______________________ / / ______ / ______________________ | / ______________________ / / ______ / ______________________
/ / ______ / / 7 7*\/ 2634 / / ______ | / / ______ / / 7 7*\/ 2634 / / ______ | | / / ______ / / 7 7*\/ 2634 / / ______ | / / ______ / / 7 7*\/ 2634 / / ______
/ 4 / 7 7*\/ 2634 14 / 135*3 / - ----- + ---------- / 4 / 7 7*\/ 2634 14 | / 4 / 7 7*\/ 2634 14 / 135*3 / - ----- + ---------- / 4 / 7 7*\/ 2634 14 | | / 4 / 7 7*\/ 2634 14 / 135*3 / - ----- + ---------- / 4 / 7 7*\/ 2634 14 | / 4 / 7 7*\/ 2634 14 / 135*3 / - ----- + ---------- / 4 / 7 7*\/ 2634 14
/ --- + 2*3 / - ----- + ---------- - ------------------------------- / \/ 10125 30375 3375* / --- + 2*3 / - ----- + ---------- - ------------------------------- | / --- + 2*3 / - ----- + ---------- - ------------------------------- / \/ 10125 30375 3375* / --- + 2*3 / - ----- + ---------- - ------------------------------- | | / --- + 2*3 / - ----- + ---------- - ------------------------------- / \/ 10125 30375 3375* / --- + 2*3 / - ----- + ---------- - ------------------------------- | 7* / --- + 2*3 / - ----- + ---------- - ------------------------------- / \/ 10125 30375 3375* / --- + 2*3 / - ----- + ---------- - -------------------------------
/ 225 \/ 10125 30375 ______________________ / / 225 \/ 10125 30375 ______________________ | / 225 \/ 10125 30375 ______________________ / / 225 \/ 10125 30375 ______________________ | | / 225 \/ 10125 30375 ______________________ / / 225 \/ 10125 30375 ______________________ | / 225 \/ 10125 30375 ______________________ / / 225 \/ 10125 30375 ______________________
/ / ______ / / / ______ | / / ______ / / / ______ | | / / ______ / / / ______ | / / ______ / / / ______
/ / 7 7*\/ 2634 / / / 7 7*\/ 2634 | / / 7 7*\/ 2634 / / / 7 7*\/ 2634 | | / / 7 7*\/ 2634 / / / 7 7*\/ 2634 | / / 7 7*\/ 2634 / / / 7 7*\/ 2634
/ 135*3 / - ----- + ---------- / / 135*3 / - ----- + ---------- | / 135*3 / - ----- + ---------- / / 135*3 / - ----- + ---------- | | / 135*3 / - ----- + ---------- / / 135*3 / - ----- + ---------- | / 135*3 / - ----- + ---------- / / 135*3 / - ----- + ----------
1 \/ \/ 10125 30375 \/ \/ \/ 10125 30375 37 | 1 \/ \/ 10125 30375 \/ \/ \/ 10125 30375 | | 1 \/ \/ 10125 30375 \/ \/ \/ 10125 30375 | \/ \/ 10125 30375 \/ \/ \/ 10125 30375
(- -- - --------------------------------------------------------------------------------- - -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------, -- + 3*|- -- - --------------------------------------------------------------------------------- - -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| + 9*|- -- - --------------------------------------------------------------------------------- - -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| + ----------------------------------------------------------------------------------- + ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------)
15 2 2 15 \ 15 2 2 / \ 15 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:
$$x_{1} = - \frac{1}{15} - \frac{\sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}{2} + \frac{\sqrt{\left|{- 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}} + \frac{8}{225} + \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{16}{3375 \sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}}\right|}}{2}$$
Puntos máximos de la función:
$$x_{1} = - \frac{\sqrt{\left|{- 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}} + \frac{8}{225} + \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{16}{3375 \sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}}\right|}}{2} - \frac{1}{15} - \frac{\sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}{2}$$
Decrece en los intervalos
$$\left(-\infty, - \frac{\sqrt{\left|{- 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}} + \frac{8}{225} + \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{16}{3375 \sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}}\right|}}{2} - \frac{1}{15} - \frac{\sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}{2}\right] \cup \left[- \frac{1}{15} - \frac{\sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}{2} + \frac{\sqrt{\left|{- 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}} + \frac{8}{225} + \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{16}{3375 \sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}}\right|}}{2}, \infty\right)$$
Crece en los intervalos
$$\left[- \frac{\sqrt{\left|{- 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}} + \frac{8}{225} + \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{16}{3375 \sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}}\right|}}{2} - \frac{1}{15} - \frac{\sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}{2}, - \frac{1}{15} - \frac{\sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}{2} + \frac{\sqrt{\left|{- 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}} + \frac{8}{225} + \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{16}{3375 \sqrt{- \frac{14}{135 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}} + \frac{4}{225} + 2 \sqrt[3]{- \frac{7}{10125} + \frac{7 \sqrt{2634}}{30375}}}}}\right|}}{2}\right]$$