Question

Solve : $(x-y{)}^2=9(x+y{)}^2=81$

Answer 1

$(x-y{)}^2=9(x-y)=\sqrt{9}x-y=3x=3+y\cdots (1\left)\right(x+y{)}^2=81x+y=\sqrt{81}x+y=93+y+y=93+2y=92y=6y=3$

Put it in $\left(1\right)$

$⟹x=6$

$x=6;y=3$