`a)(x-1)(2x-3)-(x+3)(2x-5)=4`
`⇔2x²-3x-2x+3-(2x²-5x+6x-15)=4`
`⇔2x²-3x-2x+3-2x²+5x-6x+15=4`
`⇔2x²-3x-2x-2x²+5x-6x=4-3-15`
`⇔-6x=-14`
`⇔x=7/3`
Vậy `x=7/3`
`b)(6x-3)(2x+4)+(4x-1)(5-3x)=-21`
`⇔12x²+24x-6x-12+20x-12x²-5+3x=-21`
`⇔12x²+24x-6x+20x-12x²+3x=-21+12+5`
`⇔41x=-4`
`⇔x=-4/41`
Vậy `x=-4/41`
`c)(10x+9)x-(5x-1)(2x+3)=8`
`⇔10x²+9x-(10x²+15x-2x-3)=8`
`⇔10x²+9x-10x²-15x+2x+3=8`
`⇔10x²+9x-10x²-15x+2x=8-3`
`⇔-4x=5`
`⇔x=-5/4`
Vậy `x=-5/4`
`d)x(x+1)(x+6)-x³=5x`
`⇔(x²+x)(x+6)-x³=5x`
`⇔x³+6x²+x²+6x-x³-5x=0`
`⇔7x²+x=0`
`⇔x(7x+1)=0`
`⇔`\(\left[ \begin{array}{l}x=0\\7x+1=0\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=0\\x=\dfrac{-1}{7}\end{array} \right.\)
Vậy `x∈{0;-1/7}`
