I feel way off on this one...

[Lizzie]

The question is: What is the slope of the tangent line to the curve defined by f(x)=(7x²-1)² at x=1?

I worked it out and thought it was 168... but I feel way off. Any help in understanding this would be greatly appreciated. Thank you!

 

[crestu]

Using the chain rule, f'(x) = 2(7x²-1)(2)7x = 28x(7x²-1)

Evaluating at x = 1 gives: f'(1) = 28(1)(7(1)²-1) = 28(6) = 168.

Looks like you are right

 

[Lizzie]

YAY!! Thanks very much!