What is the derivative of f(x) = x^5 * (x^2-3)^6?

1 Answer
Mar 7, 2018

5x^4(x^2-3)^6+12x^6(x^2-3)^5

Explanation:

Here:

d/dx x^5 * (x^2-3)^6

we can use product rule:

d/dx color(red)a * color(blue)b = (color(red)(a))'(color(blue)b) + (color(red)a)(color(blue)b)'

So:

d/dx color(red)(x^5) * color(blue)((x^2-3)^6)

becomes:

(color(red)x^5)'color(blue)((x^2-3)^6)+(color(red)x^5)(color(blue)((x^2-3)^6))'

Simplifying:

(5x^4)color(blue)((x^2-3)^6)+(color(red)x^5)(color(blue)((x^2-3)^6))'

d/dx color(blue)((x^2-3)^6)

We can use chain rule here:

d/dxf(x) = d/(du)f(u) * d/dx (x)

->d/dx(x^2-3)^6

becomes:

d/dx (u)^6 * d/dx (x^2-3)

=6u^5*2x

Since u=(x^2-3):

=6(x^2-3)^5*2x

d/dx color(blue)((x^2-3)^6)=12x(x^2-3)^5

Simplifying our former equation:

(5x^4)color(blue)((x^2-3)^6)+(color(red)x^5)(color(blue)((x^2-3)^6))'

becomes:

(5x^4)(x^2-3)^6+(x^5)(12x)(x^2-3)^5

Multiplying it out:

=5x^4(x^2-3)^6+12x^6(x^2-3)^5

And there we have our answer