Question

f(x) = x2 + 2x - 4, calcule f(3)

Answer 1

$f(x) = {x}^{2} + 2x - 4 \\ f(3) = {3}^{2} + 2 \times 3 - 4 \\ f(3) = 9 + 6 - 4 \\ f(3) = 11$

Answer 2

$f(x) = x2 + 2x - 4$
$f(3) = (3 \times 2) + (2 \times 3) - 4$
$f(3) = 6 + 6 - 4$
$f(3) = 12 - 4$
$f(3) = 8$