Question

If (x+y)2 =13, and xy=5, then x-2 + y-2 = ?

Answer 1

Answer:

(x+y)²=13

x²+y²+2xy=13

x²+y²+10=13

x²+y²=3

Now, x^(-2)+y^(-2)=(x²+y²)/x²y²=3/(5)²

=3/25