giúp tôi bài 1 với mọi người ơi

Đáp án + Giải thích các bước giải:

 `a)`

`(x+3)(x-3)-x(23+x)`

`= x^2-9-23x-x^2`

`= -23x-9`

`b)`

`(x+5)(x^2-5x+25)-x(x-4)^2 +16x`

`= x^3+5^3 -x(x^2-8x+16)+16x`

`= x^3 +125 -x^3 +8x^2-16x+16x`

`= 8x^2+125`

`c)`

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

`= x^2 -2x+4x-8-x^2 +6x-9`

`= 8x -17`

`d)`

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

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

`= -2x^3 -12x -8 +2x^3 -16`

`= -12x - 24`

`e)`

`(2x-1)^2 -(x+1)(x-1)-x^2+3x-1`

`= 4x^2-4x+1-x^2+1 -x^2+3x-1`

`= 2x^2 -x +1`

`g)`

`(x+1)(x^2-x+1)+(x+2)^3 -2(x-1)^3`

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

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

`= 12x^2 + 6x +11`

`h)`

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

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

`= 2x^2 -2y^2 +2x^2 +2y^2`

`=4x^2`

`i)`

`2(x-3)(x^2+3x+9)-(x+3)^3-x(x+1)(x-1)`

`= 2(x^3-27) - x^3 - 9x^2 - 27x - 27 -x(x^2-1)`

`= 2x^3 -54-x^3  -9x^2 -27x-27 -x^3 +x`

`=  -9x^2 -26x - 81`