Let F(x) = x^2 + 2x -8
Adding 1 and - 1 at equation
F(x) = x^2 + 2x + 1 - 1 -8
Rewrinting the first 1 = 1^2
F(x) = x^2 + 2x + 1^2 - 1 - 8
Now look:
x^2 + 2x + 1^2 = ( x + 1)^2
Then,
F(x) = (x + 1)^2 -1 -8
F(x) = (x + 1)^2 -9
This is the answer !
If us to want.
(x + 1)^2 -9 = ( x+1)^2 - 3^2
= ( x+ 1 -3).(x +1 +3)
= ( x - 2).(x +4)
