a) Ta có: \(\left(x^2-3x+xy-3y\right):\left(x+y\right)\)
\(=\frac{\left(x^2+xy\right)-\left(3x+3y\right)}{x+y}\)
\(=\frac{x\left(x+y\right)-3\left(x+y\right)}{x+y}\)
\(=\frac{\left(x+y\right)\left(x-3\right)}{x+y}\)
\(=x-3\)
b) Sửa đề: \(\frac{4x^2-16}{1-2x+x^2}:\frac{3x+6}{1-x}\)
Ta có: \(\frac{4x^2-16}{1-2x+x^2}:\frac{3x+6}{1-x}\)
\(=\frac{4\left(x^2-4\right)}{\left(x-1\right)^2}:\frac{3\left(x+2\right)}{-\left(x-1\right)}\)
\(=\frac{4\left(x-2\right)\left(x+2\right)}{\left(x-1\right)^2}\cdot\frac{-\left(x-1\right)}{3\left(x+2\right)}\)
\(=\frac{-4\left(x-2\right)}{3}=\frac{-4x+8}{3}\)
