Originally Posted by

**stunirvana** Hi, I couldn't find anyone around my dorm that could help me so I thought I would try a forum. Thanks for any help I receive!

My problem is:

Find the derivative:

y = (3x^4 + 1)^4 * (x^3 + 4)

According to my book the answer is 3x^2(3x^4 + 1)^3 * (19x^4 + 64x + 1)

For some reason I never can get this solution.

Here are the 2 steps in the book that really confuse me:

3x^2(3x^4 + 1)^4 + 48x^3(x^3 + 4)(3x^4 + 1)^3

to this

3x^2(3x^4 + 1)^3[3x^4 + 1 + 16x(x^3 + 4)]

I get to the first step but I do not get the second step. I think I am just overlooking something simple, but I don't see it.

Thanks!!