Well to demonstrate the answer, let's look at a basic example:
Sq root of 2^2 = ?
Well 2 ^2 = 2•2 = 4 and the square root of 4 is 2. So whenever you think of what the opposite of squaring or raising something to the value of 2, the reverse would be taking the square root of the number or expression.
So sq root of 14x • sq. root of 14x = (sq. root of 14x) ^2 which is simply 14x.
The solution is 14x.