Bài `2:`
`a)3x(2x-8)-(6x+1)(7-x)`
`=6x^2-24x-42x+6x^2-7+x`
`=12x^2-65x-7`
`b)(16x+3)(x-2)+(4x+3x)(5-4x)`
`=16x^2-32x+3x-6+7x(5-4x)`
`=16x^2-29x-6+35x-28x^2`
`=-12x^2+6x-6`
`c)(x-3)(x+3)-(x-5)^2`
`=x^2-9-x^2+10x-25`
`=10x-34`
`d)(2x-1)^3-(2x^2-5)(x+4)`
`=8x^3-12x^2+6x-1-2x^3-8x^2+5x+20`
`=6x^3-20x^2+11x+19`
Bài `3:`
`a)3x(2-5x)+15x^2-18=0`
`<=>6x-15x^2+15x^2-18=0`
`<=>6x=18`
`<=>x=3`
Vậy `x=3`
`b)(x-2)^2-(x+3)(x-5)=0`
`<=>x^2-4x+4-x^2+5x-3x+15=1`
`<=>-2x=-18`
`<=>x=-9`
Vậy `x=-9`
`c)(2x-3)(2x+3)-4x(x-6)=10`
`<=>4x^2-9-4x^2+24x=10`
`<=>24x=19`
`<=>x=19/24`
Vậy `x=19/24`