(1) is the correct answer.
Because:
=> x
2
+6x=3x
2
+4x-4 => x
2
-x-2=0 => (X-2)(x+1)=0 =>x=2; x=-1
=> x2+6x=3x2+4x-4 => x2-x-2=0 => (X-2)(x+1)=0 =>x=2; x=-1 => x2+6x=3x2+4x-4 => x2-x-2=0 => (X-2)(x+1)=0 =>x=2; x=-1