Answer
$18$
Work Step by Step
The given expression is
$=(4\sqrt{2}-\sqrt{98})^2$
Factor as square terms.
$=(4\sqrt{2}-\sqrt{49\cdot 2})^2$
Use product property of square roots.
$=(4\sqrt{2}-\sqrt{49}\cdot \sqrt{2})^2$
Simplify.
$=(4\sqrt{2}-7\sqrt{2})^2$
Factor out $\sqrt{2}$.
$=[\sqrt{2}(4-7)]^2$
Simplify.
$=[\sqrt{2}(-3)]^2$
$=(-3\sqrt{2})^2$
$=18$