If \(\rm \sqrt {\frac{x}{y}} \, + \,\frac{1}{{\sqrt 2 }}\, = \,\sqrt {\frac{y}{x}} \) and x + y = 18, then what is the value of xy?
1
80
2
45
3
56
4
72
If \(\rm \sqrt {\frac{x}{y}} \, + \,\frac{1}{{\sqrt 2 }}\, = \,\sqrt {\frac{y}{x}} \) and x + y = 18, then what is the value of xy?