Question

Find the following limit where f(x) = 4x2 − 3x.

limit
delta x --> f(x + delta x)- f(x)/delta x

can someone please help me

Answer 1

I assume you mean the limit as delta x -> 0.
I'll use delta x = h for simplicity

(f(x + h) - f(x))/h
= (4(x+h)^2 - 3(x+h) - (4x^2 - 3x))/h
= (4x^2 + 8xh + 4h^2 - 3x - 3h - 4x^2 + 3x)/h
= (8xh + 4h^2 - 3h)/h
= 8x - 3 + 4h

Limit as h->0 = 8x-3

Looks like the derivative, eh?