Solve the quadratic equation by completing the square.
x2 + 6x + 7 = 0

 from the equation  x^2 - 6x + 7 = 0 , b is equal to -6. The form should become y = (x-(b/2)^2) + c. (b/2)^2 is equal to 9. Hence,

0 = (x - 3)^2 -9 + 7 
0 = (x - 3)^2 -2
2 = (x - 3)^2

x should be equal to -1.5858 and -4.4142