`d)(3x-5)(7-5x)-(5x+2)(2-3x)=4`
`⇔21x-15x²-35+25x-(10x-15x²+4-6x)=4`
`⇔21x-15x²-35+25x-10x+15x²-4+6x=4`
`⇔(-15x²+15x²)+(21x+25x-10x+6x)-(35+4)=4`
`⇔42x-39=4`
`⇔42x=4+39`
`⇔42x=43`
`⇔x=43/42`
Vậy `x=43/42`
`g)3(2x-1)(3x-1)-(2x-3)(9x-1)=0`
`⇔(6x-3)(3x-1)-(18x²-2x-27x+3)=0`
`⇔18x²-6x-9x+3-18x²+2x+27x-3=0`
`⇔(18x²-18x²)+(-6x-9x+2x+27x)+(3-3)=0`
`⇔14x=0`
`⇔x=0`
Vậy `x=0`
`j)(2x-1)(3x+1)-(4-3x)(3-2x)=3`
`⇔6x²+2x-3x-1-(12-8x-9x+6x²)=3`
`⇔6x²+2x-3x-1-12+8x+9x-6x²=3`
`⇔(6x²-6x²)+(2x-3x+8x+9x)+(-1-12)=3`
`⇔16x-13=3`
`⇔16x=3+13`
`⇔16x=16`
`⇔x=16:16`
`⇔x=1`
Vậy `x=1`
`k)(2x+1)(x+3)-(x-5)(7+2x)=8`
`⇔2x²+6x+x+3-(7x+2x²-35-10x)=8`
`⇔2x²+6x+x+3-7x-2x²+35+10x=8`
`⇔(2x²-2x²)+(6x+x-7x+10x)+(3+35)=8`
`⇔10x+38=8`
`⇔10x=8-38`
`⇔10x=-30`
`⇔x=(-30):10`
`⇔x=-3`
Vậy `x=-3`
`m)2(3x-1)(2x+5)-6(2x-1)(x+2)=-6`
`⇔(6x-2)(2x+5)-6(2x²+4x-x-2)=-6`
`⇔12x²+30x-4x-10-12x²-24x+6x+12=-6`
`⇔(12x²-12x²)+(30x-4x-24x+6x)+(-10+12)=-6`
`⇔8x+2=-6`
`⇔8x=-6-2`
`⇔8x=-8`
`⇔x=(-8):8`
`⇔x=-1`
Vậy `x=-1`
