I need some help understanding this limit formula, could someone please explain how to solve for f(x)=x^2+1 using this formula:

Question

(f(x+Δx)-f(x))/(Δx)

Answer 1

this is how you plug it in:

[(x + Δx)^2 + 1- (x^2 + 1)]/(Δx)

Rework the equation to get:

Δx + 2x, in it should be lim as Δx goes to 0, and that would leave you with 2x, which if you used easy method, leaves you with same answer.