Answer:
[tex]D)~(x+3)^2 = 16[/tex]
Step-by-step explanation:
[tex]~~~~~~x^2 +6x -7 = 0\\\\\implies x^2+6x = 7\\\\\implies x^2 +2 \cdot 3 \cdot x +3^2 -3^2 = 7\\\\\implies x^2 +2 \cdot 3 \cdot x+3^2 = 7+3^2\\\\\implies (x+3)^2 = 7+9\\\\\implies (x+3)^2 = 16[/tex]