Question

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

Answer 1

Answer: Line 2

Explanation:

Answer 2

In completing the square, the first step is to factor out the first and second term so that the factor (x+a) is highlighted. This is seen in line 1. However, in line 2, the subtracted value should be 3 so as to compensate for the added value. This affects then line 3 as well. The answer is line 2.