\(M=\frac{x^2}{\left(x+y\right)\left(1-y\right)}-\frac{y^2}{\left(x+y\right)\left(1+x\right)}-\frac{x^2y^2}{\left(x+1\right)\left(x+y\right)}\)
\(M=\frac{x^2}{\left(x+y\right)\left(1-y\right)}-\frac{y^2-x^2y^2}{\left(x+1\right)\left(x+y\right)}\)
\(M=\frac{x^2}{\left(x+y\right)\left(1-y\right)}-\frac{y^2\left(1-x^2\right)}{\left(x+1\right)\left(x+y\right)}\)
\(M=\frac{x^2}{\left(x+y\right)\left(1-y\right)}-\frac{y^2\left(1-x\right)\left(1+x\right)}{\left(x+1\right)\left(x+y\right)}\)
\(M=\frac{x^2}{\left(x+y\right)\left(1-y\right)}-\frac{y^2\left(1-x\right)\left(1-y\right)}{\left(x+y\right)\left(1-y\right)}\)
\(M=\frac{x^2-y^2.\left(1-x-y+xy\right)}{\left(x+y\right)\left(1-y\right)}\)
\(M=\frac{x^2-y^2+xy^2+y^3-xy^3}{\left(x+y\right)\left(1-y\right)}\)
đến đây phân tích ra nhân tử chung rồi làm tiếp