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$$4 x^{3} \left(x^{3} - 4\right) + 3 x^{2} \left(x^{4} + 2\right) = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 0$$
$$x_{2} = - \frac{\sqrt{- 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}} - \frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + \frac{32}{7 \sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}}}{2} + \frac{\sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}{2}$$
$$x_{3} = \frac{\sqrt{- 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}} - \frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + \frac{32}{7 \sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}}}{2} + \frac{\sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}{2}$$
Signos de extremos en los puntos:
(0, -8)
/ 3\ / 4\
___________________________________________________________________________________________________________________ | / ___________________________________________________________________________________________________________________\ | | / ___________________________________________________________________________________________________________________\ |
/ _______________ | | / _______________ | | | | / _______________ | |
/ / ___ | | / / ___ | | | | / / ___ | |
/ / 16 10*\/ 2 4 32 | | / / 16 10*\/ 2 4 32 | | | | / / 16 10*\/ 2 4 32 | |
/ - 2*3 / -- + -------- - ---------------------- + ------------------------------------------------------------- | | / - 2*3 / -- + -------- - ---------------------- + ------------------------------------------------------------- | | | | / - 2*3 / -- + -------- - ---------------------- + ------------------------------------------------------------- | |
_________________________________________________ / \/ 49 49 _______________ _________________________________________________ | | _________________________________________________ / \/ 49 49 _______________ _________________________________________________ | | | | _________________________________________________ / \/ 49 49 _______________ _________________________________________________ | |
/ _______________ / / ___ / _______________ | | / _______________ / / ___ / _______________ | | | | / _______________ / / ___ / _______________ | |
/ / ___ / / 16 10*\/ 2 / / ___ | | / / ___ / / 16 10*\/ 2 / / ___ | | | | / / ___ / / 16 10*\/ 2 / / ___ | |
/ / 16 10*\/ 2 4 / 7*3 / -- + -------- / / 16 10*\/ 2 4 | | / / 16 10*\/ 2 4 / 7*3 / -- + -------- / / 16 10*\/ 2 4 | | | | / / 16 10*\/ 2 4 / 7*3 / -- + -------- / / 16 10*\/ 2 4 | |
/ 2*3 / -- + -------- + ---------------------- / \/ 49 49 7* / 2*3 / -- + -------- + ---------------------- | | / 2*3 / -- + -------- + ---------------------- / \/ 49 49 7* / 2*3 / -- + -------- + ---------------------- | | | | / 2*3 / -- + -------- + ---------------------- / \/ 49 49 7* / 2*3 / -- + -------- + ---------------------- | |
/ \/ 49 49 _______________ / / \/ 49 49 _______________ | | / \/ 49 49 _______________ / / \/ 49 49 _______________ | | | | / \/ 49 49 _______________ / / \/ 49 49 _______________ | |
/ / ___ / / / ___ | | / / ___ / / / ___ | | | | / / ___ / / / ___ | |
/ / 16 10*\/ 2 / / / 16 10*\/ 2 | | / / 16 10*\/ 2 / / / 16 10*\/ 2 | | | | / / 16 10*\/ 2 / / / 16 10*\/ 2 | |
/ 7*3 / -- + -------- / / 7*3 / -- + -------- | | / 7*3 / -- + -------- / / 7*3 / -- + -------- | | | | / 7*3 / -- + -------- / / 7*3 / -- + -------- | |
\/ \/ 49 49 \/ \/ \/ 49 49 | |\/ \/ 49 49 \/ \/ \/ 49 49 | | | |\/ \/ 49 49 \/ \/ \/ 49 49 | |
(----------------------------------------------------------- - ----------------------------------------------------------------------------------------------------------------------------------, |-4 + |----------------------------------------------------------- - ----------------------------------------------------------------------------------------------------------------------------------| |*|2 + |----------------------------------------------------------- - ----------------------------------------------------------------------------------------------------------------------------------| |)
2 2 \ \ 2 2 / / \ \ 2 2 / /
/ 3\ / 4\
___________________________________________________________________________________________________________________ | / ___________________________________________________________________________________________________________________\ | | / ___________________________________________________________________________________________________________________\ |
/ _______________ | | / _______________ | | | | / _______________ | |
/ / ___ | | / / ___ | | | | / / ___ | |
/ / 16 10*\/ 2 4 32 | | / / 16 10*\/ 2 4 32 | | | | / / 16 10*\/ 2 4 32 | |
/ - 2*3 / -- + -------- - ---------------------- + ------------------------------------------------------------- | | / - 2*3 / -- + -------- - ---------------------- + ------------------------------------------------------------- | | | | / - 2*3 / -- + -------- - ---------------------- + ------------------------------------------------------------- | |
_________________________________________________ / \/ 49 49 _______________ _________________________________________________ | | _________________________________________________ / \/ 49 49 _______________ _________________________________________________ | | | | _________________________________________________ / \/ 49 49 _______________ _________________________________________________ | |
/ _______________ / / ___ / _______________ | | / _______________ / / ___ / _______________ | | | | / _______________ / / ___ / _______________ | |
/ / ___ / / 16 10*\/ 2 / / ___ | | / / ___ / / 16 10*\/ 2 / / ___ | | | | / / ___ / / 16 10*\/ 2 / / ___ | |
/ / 16 10*\/ 2 4 / 7*3 / -- + -------- / / 16 10*\/ 2 4 | | / / 16 10*\/ 2 4 / 7*3 / -- + -------- / / 16 10*\/ 2 4 | | | | / / 16 10*\/ 2 4 / 7*3 / -- + -------- / / 16 10*\/ 2 4 | |
/ 2*3 / -- + -------- + ---------------------- / \/ 49 49 7* / 2*3 / -- + -------- + ---------------------- | | / 2*3 / -- + -------- + ---------------------- / \/ 49 49 7* / 2*3 / -- + -------- + ---------------------- | | | | / 2*3 / -- + -------- + ---------------------- / \/ 49 49 7* / 2*3 / -- + -------- + ---------------------- | |
/ \/ 49 49 _______________ / / \/ 49 49 _______________ | | / \/ 49 49 _______________ / / \/ 49 49 _______________ | | | | / \/ 49 49 _______________ / / \/ 49 49 _______________ | |
/ / ___ / / / ___ | | / / ___ / / / ___ | | | | / / ___ / / / ___ | |
/ / 16 10*\/ 2 / / / 16 10*\/ 2 | | / / 16 10*\/ 2 / / / 16 10*\/ 2 | | | | / / 16 10*\/ 2 / / / 16 10*\/ 2 | |
/ 7*3 / -- + -------- / / 7*3 / -- + -------- | | / 7*3 / -- + -------- / / 7*3 / -- + -------- | | | | / 7*3 / -- + -------- / / 7*3 / -- + -------- | |
\/ \/ 49 49 \/ \/ \/ 49 49 | |\/ \/ 49 49 \/ \/ \/ 49 49 | | | |\/ \/ 49 49 \/ \/ \/ 49 49 | |
(----------------------------------------------------------- + ----------------------------------------------------------------------------------------------------------------------------------, |-4 + |----------------------------------------------------------- + ----------------------------------------------------------------------------------------------------------------------------------| |*|2 + |----------------------------------------------------------- + ----------------------------------------------------------------------------------------------------------------------------------| |)
2 2 \ \ 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:
$$x_{1} = \frac{\sqrt{- 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}} - \frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + \frac{32}{7 \sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}}}{2} + \frac{\sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}{2}$$
Puntos máximos de la función:
$$x_{1} = - \frac{\sqrt{- 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}} - \frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + \frac{32}{7 \sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}}}{2} + \frac{\sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}{2}$$
Decrece en los intervalos
$$\left(-\infty, - \frac{\sqrt{- 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}} - \frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + \frac{32}{7 \sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}}}{2} + \frac{\sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}{2}\right] \cup \left[\frac{\sqrt{- 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}} - \frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + \frac{32}{7 \sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}}}{2} + \frac{\sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}{2}, \infty\right)$$
Crece en los intervalos
$$\left[- \frac{\sqrt{- 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}} - \frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + \frac{32}{7 \sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}}}{2} + \frac{\sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}{2}, \frac{\sqrt{- 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}} - \frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + \frac{32}{7 \sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}}}{2} + \frac{\sqrt{\frac{4}{7 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}} + 2 \sqrt[3]{\frac{10 \sqrt{2}}{49} + \frac{16}{49}}}}{2}\right]$$