Answer
$6\sqrt{2}$
Work Step by Step
The given expression is
$=\sqrt{b^2-4ac}$
The given values are
$a=-2,b=4$ and $c=7$
Substitute all the values into the expression.
$=\sqrt{(4)^2-4(-2)(7)}$
Simplify.
$=\sqrt{16+56}$
Subtract.
$=\sqrt{72}$
$=6\sqrt{2}$.
