\(a,=x^2-mx-nx+mn=x\left(x-m\right)-n\left(x-m\right)=\left(x-n\right)\left(x-m\right)\\ b,=a\left(x-y\right)-b\left(x-y\right)+\left(a-b\right)\\ =\left(x-y\right)\left(a-b\right)+\left(a-b\right)=\left(a-b\right)\left(x-y+1\right)\)
b: \(=a\left(x-y\right)-b\left(x-y\right)+a-b\)
\(=\left(x-y+1\right)\left(a-b\right)\)
a) \(x^2-\left(m+n\right)x+mn=\left(x^2-n\cdot x\right)-\left(m\cdot x-m\cdot n\right)=x\left(x-n\right)-m\left(x-n\right)=\left(x-m\right)\left(x-n\right)\)
b) \(ax+by+a-bx-ay-b\)
\(=\left(ax-ay+a\right)-\left(bx-by+b\right)\)
\(=a\left(x-y+1\right)-b\left(x-y+1\right)\)
\(\left(a-b\right)\left(x-y+1\right)\)
