complete the square of x2−6x+8
Ok!
x^2 - 6x + 8
= x^2 - 6x + 36 - 36 + 8
= (x - 6)^2 - 28
x2 -6x +8 +1-1 = (x2 -6x +9) -1
= (x-3)2 - 1
