Solve for x by completing the square:
x^2+10x+9=0
x = 1, x = 9
x = - 1, x = - 9
x = 11, x = - 21
x = - 11, x = 21
x^2+10x+9=0
x = 1, x = 9
x = - 1, x = - 9
x = 11, x = - 21
x = - 11, x = 21