Question

How to do a? and possibly b...

Answer 1

Answer:

u'=2(2t³-21t)³(6t-21)

Step-by-step explanation:

For a. they want you take the derivative of that function but in terms of t, which means you have to plug in that x=... part at some point.

You can either plug it in first and then take a derivative or take the derivative first then plug it in. But remember if you take a derivative first then u'=2x³(x') due to the chain rule; so you'd need to plug in the derivative of x anyways. It's really just a matter of preference at that point.

Doing it either way gives us:

u'=2(2t³-21t)³(6t-21)

For b. you just need to plug in 2 and simplify to get your answer there.