Answer
$42x$.
Work Step by Step
The given expression is
$=(36x)^{\frac{1}{2}}(49x)^{\frac{1}{2}}$
Rewrite as square terms.
$=(6^2x)^{\frac{1}{2}}(7^2x)^{\frac{1}{2}}$
Raise each factor to the second power.
$=6^{(2\cdot \frac{1}{2})}x^{\frac{1}{2}}7^{(2\cdot \frac{1}{2})}x^{\frac{1}{2}}$
Simplify.
$=6x^{\frac{1}{2}}7x^{\frac{1}{2}}$
Add exponents of powers with the same base.
$=6\cdot 7x^{\frac{1}{2}+\frac{1}{2}}$
Simplify.
$=42x^{\frac{1+1}{2}}$
$=42x^{\frac{2}{2}}$
$=42x$.