## anonymous 4 years ago find the derivative of x^3 at x=-2 algebraically, jot my memory, do you use f(x+h)-f(x)/h?

1. phi

Unless you are deriving the various formulas, there is no reason to use the fundamental approach. Use the exponent rule: $\frac{ d x^n}{dx}= n x^{n-1}$

2. phi

once you have found the derivative, replace x with -2 and evaluate it to answer the question

3. precal

Use the power rule. Easiest rule in calculus to remember. By the way phi already stated it above.

4. anonymous

ok thank you soo, x^3 using the power rule, 3x^2 is the derivative, then plugging in x=-2 gives us 3(-2)^2=12?

5. phi

yes

6. anonymous

thank you phi and pre cal, im in calc 1 and it can be confusing at times, I guess the power rule is a lifesaver, much thanks

7. precal

use calculus notation for example y prime or f prime of x

8. anonymous

ok like this right f'(x)

9. precal

yes f'(-2)=12

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