`\text{e)} x^2 (x - y) - y (y - x)`
`= x^2 (x - y) + y (x - y)`
`= (x^2 + y) (x - y)`
`\text{f)} 2x (x - 4) - 5 (4 - x) - (2x + 5) (7 - 5x)`
`= 2x (x - 4) + 5 (x - 4) - (2x + 5) (7 - 5x)`
`= (x - 4) (2x + 5) - (2x + 5) (7 - 5x)`
`= (2x + 5) (x - 4 - 7 + 5x)`
`= (2x + 5) (6x - 3)`
`\text{g)} 36x^2 - (3x - 2)^2`
`= (6x)^2 - (3x - 2)^2`
`= (6x + 3x - 2) (6x - 3x + 2)`
`= (9x - 2) (3x + 2)`
`\text{h)} 16x^2 - 24xy + 9x^2`
`= 16x^2 + 9x^2 - 24xy`
`= 25x^2 - 24xy`
`= x (25x - 24y)`
`\text{i)} xy + 1 - x - y`
`= (xy - y) + (1 - x)`
`= y (x - 1) - (x - 1)`
`= y (x - 1)`
`\text{k)} 49 - x^2 + 2xy - y^2`
`= 49 - x^2 + 2 (-x) (-y) - y^2`
`= 7^2 - (- x - y)^2`
`= (7 + x + y) (7 - x - y)`
