Đáp án: + Giải thích các bước giải:
`a, y^2 (x^2 + y) - zx^2 - zy`
`= y^2 (x^2 + y) - z(x^2 + y)`
`= (x^2 + y)(y^2 - z)`
`b, (2x + 3)^2 - (x - 1)^2`
`= [(2x + 3) - (x - 1)][(2x +3) + (x - 1)]`
`= (2x + 3 - x + 1)(2x + 3 + x - 1)`
`= (x + 4)(3x + 2)`
`c, x^4 - x^3 - x^2 + 1`
`= (x^4 - x^3) - (x^2 - 1)`
`= x^3 (x -1) - (x - 1)(x + 1)`
`= (x - 1)[x^3 - (x + 1)]`
`= (x - 1)(x^3 - x - 1)`
`d, x^2 y + xy^2 - x - y`
`= (x^2 y + xy^2) - (x + y)`
`= xy(x + y) - (x +y)`
`= (x + y)(xy - 1)`
`e, ax^2 + ay - bx^2 - by`
`= (ax^2 + ay) - (bx^2 + by)`
`= a(x^2 + y) - b(x^2 + y)`
`= (x^2 + y)(a - b)`