a: 3(x-y)-x(x-y)=(x-y)(3-x)
b: =(x-y)(x+y)+4(x-y)
=(x-y)(x+y+4)
c: =(5x-1)^2-y^2
=(5x-1-y)(5x-1+y)
d: =4y(x^2-7x+10)
=4y(x-2)(x-5)
b) \(x^2-y^2+4x-4y\)
\(=\left(x^2-y^2\right)+\left(4x-4y\right)\)
\(=\left(x+y\right)\left(x-y\right)+4\left(x-y\right)\)
\(=\left(x-y\right)\left[\left(x+y\right)+4\right]\)
\(=\left(x-y\right)\left(x+y+4\right)\)
c) \(1-10x+25x^2-y^2\)
\(=\left(25x^2-10x+1\right)-y^2\)
\(=\left(5x-1\right)^2-y^2\)
\(=\left(5x-1-y\right)\left(5x-1+y\right)\)
d) \(4x^2y-28xy+40y\)
\(=4y\left(x^2-7x+10\right)\)
\(=4y\left(x^2-5x-2x+10\right)\)
\(=4y\left[x\left(x-5\right)-2\left(x-5\right)\right]\)
\(=4y\left(x-5\right)\left(x-2\right)\)
