`x^(2) + xy + y^(2) =100`

If x:y::5:2, then (x ^(2) - xy + y ^(2))/( x ^(2) + xy + y ^(2)) = ?

Simplify the following : 3xy^(2) - 5x^(2)y + 7xy - 9xy^(2) - 4xy + 6x^(2)y

The HCF of x^(2) - xy - 2y^(2) and 2x^(2) - xy - y^(2) is

Add 9x^(2) + 13xy + y^(2) and 6y^(2) - 2xy + 21x^(2)

What should be added to product of (x ^(2) + xy - y ^(2)) and (x ^(2) - xy + y ^(2)) to get x ^(2) y ^(2)