`a)8x-2y`
`=2(4x-y)`
`b)10x^2(x-y)-11y(y-x)`
`=10x^2(x-y)+11y(x-y)`
`=(x-y)(10x^2+11y)`
`c)x^2+4x`
`=x(x+4)`
`d)25x^2-(x-2y+z)-15x(x-2y)-15xz`
`=25x^2-(x-2y+z)-15x^2+30xy-15xz`
`=25x^2-(x-2y+z)-(15x^2-30xy+15xz)`
`=25x^2-(x-2y+z)-15x(x-2y+z)`
`=(x-2y+z)(25x^2-15x)`
`=(x-2+z)(5x-3).5x`
`e)3y(x-y)-5x(y-x)`
`=3y(x-y)+5x(x-y)`
`=(x-y)(3y+5x).`
