Question

HELP! Use the long definition to compute the derivative 2x^2+10x^2, a=3

Answer 1

\[{d(2x^2 + 10x^2) \over dx} = \lim_{\large x \to 3}{2x^2 + 10x^2 + 2(x + \Delta x )^2 + 10(x + \Delta x)^2 \over \Delta x}\]

Answer 2

I know how to set it up, but I couldn't get it to equal the correct answer, which is 22. I'm not sure what I did wrong.

Answer 3

OH wow, just kidding. I had been doing the (h+3), but when there is an a, you can do f(x)-f(a)/x-a. Then that would equal

[(2x^2+10x^2)+(2*3^2+10*3^2)]/x-3 ?

The next step would be 2x^2+10x^2+18+90/x-3

2x^2+10x^2+108/x-3

2x+10x+108/-3

Then if you plug in 3 that's the wrong answer...what am I doing wrong? I need a step by step please