Marvin was completing the square, and his work is shown below. Identify the line where he made his mistake.
f(x) = 2x^2 − 8x + 5
Line 1: f(x) = 2(x^2 − 8x) + 5
Line 2: f(x) = 2x^2 − 8x + 16) + 5 − 32
Line 3: f(x) = 2(x − 4)^2 − 27

Question

Marvin was completing the square, and his work is shown below. Identify the line where he made his mistake.
f(x) = 2x^2 − 8x + 5
Line 1: f(x) = 2(x^2 − 8x) + 5
 Line 2: f(x) = 2x^2 − 8x + 16) + 5 − 32 
Line 3: f(x) = 2(x − 4)^2 − 27

jdoe0001 · Answer

$\large \begin{array}{llll}
\qquad f(x) = 2x^2 - 8x + 5\
Line 1: f(x) = {\color{blue}{ 2}}(x^2 - {\color{blue}{ 8}}x) + 5\
 Line 2: f(x) = 2x^2 - 8x + 16) + 5 - 32 \
Line 3: f(x) = 2(x - 4)^2 − 27
\end{array}$

what do you think?