Question

Rút gọn biểu thức: A=(x-y)^2+(x+y)^2-2(x+y)(x-y)-4(y^2-1)

Answer 1

\(A=\left(x-y\right)^2+\left(x+y\right)^2-2\left(x+y\right)\left(x-y\right)-4\left(y^2-1\right)\)

   \(=\left(x-y-x-y\right)^2-4\left(y^2-1\right)\)

   \(=\left(-2y\right)^2-4y^2+4=4\)