2n^2+4n+4=16+4 completing the square

Question

completing the square

Answer 1

n=-4 or 2

2n^2 +4n + 4 = 16 +4 = 20

n^2 +2n +2 = 10

n^2 +2n +1 = 10-1 = 9

(n+1)^2 = 3^2

n+1 = + or - 3

n = -1 + or -3

n = -4 or 2