Question

x-y=7 xy=9 find the value of x2+y2

Answer 1

We have formula
(x-y)² =x²+y²-2xy

so x²+ y² = (x-y)² +2xy

Here we have (x-y) =7
and xy=9

so x²+y² = (7)² +2×9

x²+y² = 49+18
x²+y² = 67