Answer:
Line 2
Step-by-step explanation:
Madeline was completing the square, and her work is shown below
f(x) = 3x2 + 6x − 7
Line 1: f(x) = 3(x2 + 2x) − 7
Line 2: f(x) = 3(x2 + 2x + 1) − 7 − 1
Line 3: f(x) = 3(x + 1)2 − 8
\(f(x) = 3x^2 + 6x - 7\)
In completing the square method we need x^2 alone
Take out 3 from first two terms
\(f(x) = (3x^2 + 6x) - 7\)
\(f(x) = 3(x^2 + 2x) - 7\)
In completing the square method, we take middle term 2 , divide by 2 and then square it
2/2 =1
1^2 = 1
Now add and subtract 1
\(f(x) = 3(x^2 + 2x +1 - 1) - 7\)
Take out -1 , multiply with 3
\(f(x) = 3(x^2 + 2x +1) -3- 7\)
\(f(x) = 3(x^2 + 2x +1) -10\)
Madeline made a mistake in Line 2 . she forgot to multiply 3 with -1
