Question #a62bb

2 Answers
Jan 9, 2018

dy/dx=15x^2(1+x^3)^4dydx=15x2(1+x3)4

Explanation:

.

y=(1+x^3)^5y=(1+x3)5

u=1+x^3u=1+x3

(du)/dx=3x^2dudx=3x2

y=u^5y=u5

dy/(du)=5u^4dydu=5u4

Using Chain Rule:

dy/dx=dy/(du)*(du)/dxdydx=dydududx

dy/dx=5u^4(3x^2)dydx=5u4(3x2)

dy/dx=5(1+x^3)^4(3x^2)dydx=5(1+x3)4(3x2)

dy/dx=15x^2(1+x^3)^4dydx=15x2(1+x3)4

Jan 9, 2018

f'(x)=15x^14+60x^11+90x^8+60x^5+15x^2

Explanation:

You need to know two rules: the power rule and the chain rule.
The power rule states that if f(x)=x^n, then f'(x)=nx^(n-1)
The chain rule states that if f(x)=g(x) , then the derivative of f(x) is the derivative of g(x) times the derivative of x.

Therefore, if f(x)=(1+x^3)^5, then
f'(x)=5(1+x^3)^4xx(3x^2) or
f'(x)=15x^2(1+x^3)^4
You could of course expand this to get:
f'(x)=15x^14+60x^11+90x^8+60x^5+15x^2

We're of course, saying that f(x)=y