# How do you find the missing number or term to make a perfect square trinomial. y^2 - 7y +___ ?

May 29, 2015

General form for a perfect (binomial) square:
${\left(y + a\right)}^{2} = {y}^{2} + 2 a y + {a}^{2}$

Given y^2-7y+ ?

$\left(- 7 y\right) = 2 a y$

$\rightarrow a = \left(- \frac{7}{2}\right)$

$\rightarrow {a}^{2} = \frac{49}{4}$

The missing term is $\frac{49}{4}$