Question

 

bài 2

a,(3-xy^2)^2 - (2+xy^2)^2

b,(x-y)(x^2+xy+y^2)-(x+y)(x^2-xy+y^2)

c,(x-3)^3 + (2-x)^3

bài3

a,8x^3yz+12x^3yz+6xyz+yz

b,25(x+5)^2 - 9(x+7)^2

c,3x^2 + 4x - 4

d,2x(x-5) - x^2 + 5x

 

Answer 1

`(3 - xy^2)^2 - (2 + xy^2)^2`

`= 9 - 6xy^2 + x^2 y^4 - (4 + 4xy^2 + x^2 y^4)`

`= 9 - 6xy^2 + x^2 y^4 - 4 - 4xy^2 - x^2 y^4`

`= 5 - 10xy^2`

`(x-y)(x^2+xy+y^2)-(x+y)(x^2-xy+y^2)`

`= x^3 - y^3 - (x^3 + y^3) `

`= x^3 - y^3 - x^3 - y^3`

`= -2y^3`

`(x-3)^3 + (2-x)^3`

`= x^3 - 9x^2 + 27x - 27 + 8 - 12x + 6x^2 - x^3`

`= -3x^2 + 15x - 19`

 

Answer 2

Sửa đề: `8x^3yz+12x^2yz+6xyz+yz`

`= yz(8x^3 + 12x^2 + 6x + 1) `

`= yz(2x + 1)^3`

`25(x+5)^2 - 9(x+7)^2`

`= 5^2 . (x+5)^2 - 3^2 .(x+7)^2`

`= (5x + 25)^2 - (3x + 21)^2`

`= (5x + 25 - 3x - 21)(5x + 25 + 3x + 21) `

`= (2x + 4)(8x + 46) `

`= 4(x + 2) (4x + 23) `

`3x^2 + 4x - 4`

`= 3x^2 + 6x - 2x - 4`

`= (3x^2 + 6x) - (2x + 4) `

`= 3x(x + 2) - 2(x+2) `

`= (3x - 2)(x+2) `

`2x(x-5) - x^2 + 5x`

`= 2x(x-5) - (x^2 - 5x)`

`= 2x(x-5) - x(x - 5)`

`= x(x-5) `