Finding a point on xy-plane?

Question

such that the first coordinate plus the second coordinate equals 3, and the square of the first coordinate minus the square of the second coordinate equals -9.

Answer 1

x+y=3
x^2-y^2=-9 so (x+y)(x-y) = -9
(x-y)= -3 and
x+y=3 so x= 0 and y =3

Answer 2

x+y=3

x^2-y^2=-9 = (x+y)(x-y)=-9 = 3(x-y)=-9

x-y=-3
by adding the two equation x=0
by subistitution y=3