x^2+6x=7
take 1/2 of 6 and square it (3^2=9)
add that to both sides
x^2+6x+9=7+9
x^2+6x+9=16
factor perfect square
(x+3)^2=16
square root both sides
remembe to take the positive and negative square roots
x+3=+/-4
minus 3 from both side
x=+/-4-3
x=-7 or 1
A is answer
