a; 2x(7x+5)-7x(2x-3)=93
⇔14x²+10x-14x²+21x=93
⇔31x=93
⇔x=3
vậy x=3
b; 5x(3-7x)+7x(5x+6)=114
⇔15x-35x²+35x²+42x=114
⇔57x=114
⇔x=2
vậy x=2
c; (12x-5)(4x-1)+(3x-7)(1-16x)=18
⇔(48x²-12x-20x+5)+(3x-48x²-7+112)=18
⇔48x²-12x-20x+5+3x-48x²-7+112=18
⇔-29x=18-5+7-112
⇔-29x=-92
⇔x=$\frac{92}{29}$
vậy x=$\frac{92}{29}$
d; (2x+3)(x-4)+(x-5)(x-2)=(3x-5)(x-4)
⇔2x²-8x+3x-12+x²-2x-5x+10=3x²-12x-5x+20
⇔2x²-8x+3x+x²-2x-5x-3x²+12x+5x=20+12-10
⇔5x=22
⇔x=$\frac{22}{5}$
vậy x=$\frac{22}{5}$
j; (3x²-x+1)(x-1)+x²(4-3x)=$\frac{5}{2}$
⇔3x³-3x²-x²+x+x-x+4x²-3x³=$\frac{5}{2}$
⇔-x=$\frac{5}{2}$
vậy x=$\frac{5}{2}$
g;2x²+3(x-1)(x+1)=5x(x-1)
⇔2x²+3(x²+x-x-1)=5x²-5x
⇔2x²+3x²+3x-3x-5x²+5x=3
⇔5x=3
⇔x=$\frac{3}{5}$
vậy x =$\frac{3}{5}$
