Madeline was completing the square and her work is shown below. Identify the line where she made her mistake.. . f(x) = 3x^2 + 6x − 7. Line 1: f(x) = 3(x + 2x) − 7. Line 2: f(x) = 3(x + 2x + 1) − 7 − 1. Line 3: f(x) = 3(x + 1)2 − 8