So the square of x is-16 >; =0; 16-x >: =0 square, simultaneous expression, x= plus or minus 4.

And because the denominator cannot be zero and 8-2x is not equal to 0, X is not equal to 4, so x=-4.

Bring X=-4 into the original formula y and get y=-9/ 16. So xy=9/4, and the square root of xy = 3/2.