Question

The number that is to be added to $x^2+12x$ to make it a perfect square is .

• A. 144
• B. 36
• C. 18
• D. 72

Answer 1

The correct option is B 36

To make $x^2+12x$ a perfect square, divide the coefficient of x by 2 and the add the square of the result to make this a perfect square.
Hence $\frac{12}{2}=6$ and $6^2=36.$
$\Rightarrow$ We should add 36 to make $x^2+12x$ a perfect square.