Question

x-y=9
xy=10
x la a 2 + y la a 2 = ?

Answer 1

x=9+y
xy=10
(9+y)*y=10
y=1
x=10
10²+1²=100+1=101

Answer 2

$x-y=9$ /²
$(x-y)^{2} = 9^{2}$
$x^{2} -2xy+ y^{2} =81$
$x^{2} -2*10+ y^{2} =81$
$x^{2} +y^{2} =81+20$
$x^{2} +y^{2} =101$