Question

x2 + y2 + x2 - 4y2=???

Answer 1

$x^{2} + y^{2} + x^{2} - 4 y^{2} x^{2} + x^{2} + y^{2} -4 y^{2} 2 x^{2} -3 y^{2}$

Bons estudos!