Evaluate the limit lim_(h rarr 0) {(x-h)^3-x^3}/h?

1 Answer
Sep 14, 2017

lim_(h rarr 0) {(x-h)^3-x^3}/h = -3x^2

Explanation:

We seek:

L = lim_(h rarr 0) {(x-h)^3-x^3}/h

Therefore:

L = lim_(h rarr 0) {x^3-3x^2h+3xh^2-h^3-x^3}/h
\ \ \ = lim_(h rarr 0){-3x^2h+3xh^2-h^3}/h

\ \ \ = lim_(h rarr 0)-3x^2+3xh-h^2

\ \ \ = -3x^2 +0 + 0

\ \ \ = -3x^2