4x-20 12x²y-3xy²+18x²y³ 3y(y.2x)+6y(2x-y) 7x(x-1)+5y(x-1) 2(x-1)-y(1-x)

`a,`

`4x-20`

`= 4(x-5)`

`b,` 

`12x^2 y -3xy^2 +18x^2 y^3`

`=  3xy(4x-y+6xy^2)`

`c,` 

`3y(y.2x)+6y(2x-y)`

`= 3y^2 . 6xy +6y(2x-y)`

`= 6y(3xy^2 +2x-y)`

`d,` 

`7x(x-1)+5y(x-1)`

`=(x-1)(7x+5y)`

`e,`

`2(x-1)-y(1-x)`

`= 2(x-1)+y(x-1)`

`=(x-1)(2+y)`