Answer
$2\sqrt{5}$
Work Step by Step
The given expression is
$=\sqrt{b^2-4ac}$
The given values are
$a=1,b=6$ and $c=4$
Substitute all the values into the expression.
$=\sqrt{(6)^2-4(1)(4)}$
Simplify.
$=\sqrt{36-16}$
Subtract.
$=\sqrt{20}$
$=2\sqrt{5}$.
