Answer
The answer is $29|x| \sqrt {5}$ .
Work Step by Step
Taking the required square factors outside the square root and adding the terms:
$2 \sqrt {20x^{2}}+5\sqrt {125x^2} =2\sqrt {(2^2).5.x^2 }+5\sqrt {5^2.5.x^2}$
$=2(2)|x|\sqrt {5}+25|x|\sqrt {5}$
$=4|x|\sqrt {5}+25|x|\sqrt {5}$
$=29|x|\sqrt {5}$
