3. Find the greatest and least values of the function $y=3 x^{4}+4 x^{3}+34$ on the interval $[-2 ; 1]$.
Solution: $y=3 x^{4}+4 x^{3}+34 ; y^{\prime}=12 x^{3}+12 x^{2}=12 x^{2}(x+1)$

![](https://cdn.mathpix.com/cropped/2024_05_06_8eeeb8d6ace591217257g-14.jpg?height=120&width=571&top_left_y=1362&top_left_x=1416)
$x=0 ; x=-1 . y(-2)=50 ; y(1)=41 ; y(-1)=33$.