Cần gấp ạ bài 5 ạ !!!

Bài `5`:

`1)`

`A=3x(x^2 -2x+3)-x^2 (3x-2)+5(x^2 -x)`

`=3x^3 - 6x^2 +9x -3x^3 +2x^2 +5x^2 -5x`

`=(3x^3 -3x^3) + (-6x^2 + 2x^2 +5x^2) + (9x-5x)`

`=x^2 +4x`

`=4^2 +4.4`

`=16+16`

`=32`

`2)`

`B=3a^2 (a^2 -5)+a(-3a^3 +4a)+6a^2`

`=3a^4 - 15a^2 - 3a^4 + 4a^2 +6a^2`

`=(3a^4 - 3a^4) + (-15a^2 + 4a^2 +6a^2)`

`=-5a^2`

`=-5.(-5)^2`

`=-5.25`

`=-125`

`3)`

`C=(x-3)(x+7)-(2x-5)(x-1)`

`=x^2 +4x-21-2x^2 +7x-5`

`=(x^2 -2x^2) + (4x+7x) + (-21-5)`

`=-x^2 +11x - 26 (1)`

Trường hợp `1: x=0`

`(1)=>-0^2 +11.0-26=-26`

Trường hợp `2: x=-1`

`(1)=>-(-1)^2 + 11.(-1) -26 = -1 -11-26=-38`

`4)`

`D=(3x+5)(2x-1)+(4x-1)(3x+2)`

`=6x^2 +7x-5+12x^2 +5x-2`

`=(6x^2 +12x^2) + (7x+5x) + (-5-2)`

`=18x^2 + 12x-7 (2)`

`|x|=2<=>[(x=2),(x=-2):}`

Trường hợp `1: x=2`

`(2)=>18.2^2 + 12.2 -7=72 + 24 -7=89`

Trường hợp `2: x=-2`

`(2)=>18.(-2)^2 + 12.(-2) -7=72-24-7=41`.