Đáp án+Giải thích các bước giải:
`1)`
`a) (x^2 + 2xy -3)(-xy)`
`=-x^3y - 2x^2y^2 + 3xy`
`b) (5x-2y)(x^2-xy+1)`
`=5x^3 - 5x^2y + 5x -2x^2y+2xy^2 - 2y`
`=5x^3 - 7x^2y + 5x - 2y+2xy^2`
`c) (1/2x-1)(2x-3)`
`= x^2 - 3/2x - 2x + 3`
`=x^2 -7/2x + 3`
`d) (x-1/2)(x+1/2)(4x-1)`
`=(x^2 - 1/4 )(4x-1)`
`= 4x^3 - x^2 -x +1/4`
`2)`
`a) 3x(x-2)-5x(1-x)-8(x^2 - 3)`
`= 3x^2 -6x - 5x + 5x^2 - 8x^2 + 24`
`=(3x^2 + 5x^2 - 8x^2)-(6x+5x)+24`
`= -11x + 24`
`b) 2x(3x^3-x)-4x^2(x-x^2+1)+(x-3x)^2 .x`
`= 6x^4 - 2x^2 - 4x^3 + 4x^4 - 4x^2 + (-2x )^2 .x`
`=6x^4 - 2x^2 - 4x^3 + 4x^4 - 4x^2 + 4x^3`
`=(4x^4+6x^4) +( - 4x^3 +4x^3)-(2x^2 + 4x^2)`
`= 10x^4 -6x^2`
`c) 2(x-y)(x+y)+(x+y)^2 +(x-y)^2`
`=[(x+y)+(x-y)]^2`
`=(x+y+x-y)^2`
`=(2x)^2`
`=4x^2`
