From $\dfrac{x+y}{x-y} + \dfrac{x-y}{x+y} = \dfrac{5}{2}$ together with $x^2 + y^2 = 90$, we obtain —

Question

Accepted Answer

$x^2 - y^2 = 72$

Answer

$x^2 - y^2 = 81$

Answer

$x^2 - y^2 = 18$

Answer

$x^2 - y^2 = 90$

From x+yx−y+x−yx+y=52\dfrac{x+y}{x-y} + \dfrac{x-y}{x+y} = \dfrac{5}{2}x−yx+y​+x+yx−y​=25​ together with x2+y2=90x^2 + y^2 = 90x2+y2=90, we obtain —