## Introductory Algebra for College Students (7th Edition)

$x^2+10x+25 \Rightarrow (x+5)^2$
The third term of a perfect square trinomial is equal to the square of half the coefficient of the middle term. Hence, to complete the square of the given expression $x^2+10x ,$ the third term must be \begin{array}{l}\require{cancel}\left( \dfrac{10}{2} \right)^2\\\\=\left( 5 \right)^2\\\\= 25 .\end{array} Hence, $x^2+10x+25 \Rightarrow (x+5)^2 .$