`@` Angelmare

Đáp án:

6A:

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

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

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

`3x=3`

`x=1`

Vậy `x=1`

b) `3(1-4x)(x-2)+4(3x+1)(x+2)=24`

`(3-12x)(x-2)+(12x+4)(x+2)=24`

`3x-6-12x^2+24x+12x^2+24x+4x+8=24`

`(3x+24x+4x+24x)-(6-8)-(12x^2-12x^2)=24`

`55x+2=24`

`55x=22`

`x=2/5`

Vậy `x=2/5`

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

`(x^2+3x+2)(x+3)-x^3-8x^2-16x=6`

`x^3+3x^2+3x^2+9x+2x+6-x^3-8x^2+16x=6`

`-2x^2+27x=0`

`x(-2x+27)=0`

`to x=0` hoặc `-2x+27=0`

`to x=0` hoặc `-2x=-27`

`to x=0` hoặc `x=27/2`

Vậy `x in {0;27/2}`

d) `(x+1)(x^2+2x+4)-x^2(x+3)+8=0`

`x^3+2x^2+4x+x^2+2x+4-x^3-3x^2+8=0`

`6x=-12`

`x=-2`

Vậy `x=-2`

6B:

a) `(2x-3)(x-2)-x(2x+1)-6=0`

`2x^2-4x-3x+6-2x^2-x-6=0`

`-8x=0`

`x=0`

Vậy `x=0`

b) `5(2x-1)(x+2)-2(5x-3)(x+2)=5`

`(10x-5)(x+2)-(10x-6)(x+2)=5`

`10x^2+20x-5x-10-10x^2-20x+6x+12=5`

`x+2=5`

`x=3`

Vậy `x=3`