Respuesta :

coolstick
Expanding the limit, we get (x^2+2x∆x+∆x^2-2x-2∆x+1-x^2+2x-1)/∆x

Crossing the 1s , the 2xs, and the x^2s out, we get

(2x∆x+∆x^2-2∆x)/∆x

Dividing the ∆x, we get 
2x+∆x-2. 

Making the limit of ∆x=0, we get 2x-2.