Question

(picture) is this the correct way to solve 19?

Answer 1

I cant see your work very clearly so I'll work it out below:-

f(x + Δx) = (x + Δx)^2 - 2(x + Δx) - 3

= x^2 + 2x(Δx) + (Δx)^2 - 2x - 2(Δx) - 3

= x^2 - 2x + (Δx)^2 + 2x(Δx) - 2(Δx) - 3