Question

If f(x) = x2 + 2x, which expression represents f(x + 2)?

Answer 1

f(x) = x^2 + 2x

To get f(x + 2), we just plug in the x + 2 where ever there's an x

f(x + 2) = (x + 2)^2 + 2(x + 2)

f(x + 2) = x^2 + 4x + 4 + 2x + 4

f(x + 2) = x^2 + 6x + 8

Answer 2

x^2 + 6x + 8.

Explanation:

We replace the x in f(x) by x + 2 then simplify.

f(x+2) = (x + 2)^2 + 2(x + 2)

= (x + 2)(x + 2) + 2(x + 2)

= (x + 2(x + 2 + 2)

= (x + 2(x + 4)

= x^2 + 6x + 8.