Answer
$(\frac{b}{2})^2$
Work Step by Step
The coefficient of x is b.
Adding the square of half the coefficient creates a perfect square.
$(b\div2)^2=(\frac{b}{2})^2$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.