Answer
$b^{2}-4ac=9$
Work Step by Step
$a=2,b=7,c=5$
$ b^{2}-4ac\qquad$ ...substitute $2$ for $a,\ 7$ for $b$ and $5$ for $c$.
$=7^{2}-4\cdot 2\cdot 5\qquad$ ...evaluate $7^{2}$
$=49-4\cdot 2\cdot 5\qquad$ ...multiply before subtracting
$=49-40$
$=9$
