Solve. Do not use decimals.
x^2+xy=3
3x^2+2xy-y^2=7
well, we know that xy = 3-x^2
so
3 x2 +2 (3-x^2) -7 = y^2
3 x^2 + 6 -2 x^2 -7 = y^2
x^2 -1 = y^2
x^2+xy=3
3x^2+2xy-y^2=7
so
3 x2 +2 (3-x^2) -7 = y^2
3 x^2 + 6 -2 x^2 -7 = y^2
x^2 -1 = y^2