Solve. Do not use decimals.

Question

x^2+xy=3
3x^2+2xy-y^2=7

Answer 1

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