Question

if y=u^4 + 5u^2, where u= x^5+2x^2+1, find dy/dx. Leave your answer in terms of u and x.

Answer 1

@AaronAndyson

Answer 2

@ganeshie8

Answer 3

use chain rule

Answer 4

I got this:
4(x^5+2x^2+1)^3(5x^4+4x) + 5(2(x^5+2x^2+1)(5x^4+4x)

Answer 5

thats right! but the question clearly tells us to leave the answer in terms of "u" and "x"

Answer 6

y=u^4 + 5u^2

dy/dx = 4u^3 du/dx + 5(2u) du/dx
= (4u^3+10u) du/dx
= (4u^3+10u)(5x^4+4x)

Answer 7

oohh.. so we sub it

Answer 8

leave it like that. i don't think you need to replace "u"

Answer 9

thanks!!! :)