85(2) \((x\ne\pm\frac52)\): \[ 3x(2x-5)-(28-53x)=4x(2x+5) \] \[ (x-2)(x-7)=0 \] \[ \boxed{x=2;\ 7} \]
86(1) \((x\ne\pm\frac12)\): \[ -6(2x+1)+9(2x-1)=12x^2-15 \] \[ 6x(2x-1)=0 \] \[ \boxed{x=0} \] \(\frac12\) не входит в ОДЗ.
91(2) \((x\ne2,4)\): \[ 8+(3x-1)(x-4)=4(x-2) \] \[ 3x^2-17x+20=0 \] \[ x=4;\ \frac53 \] \[ \boxed{x=\frac53} \]
1(а) \((x\ne\pm\frac12)\): \[ 7(2x+1)^2-3(2x-1)^2-56=0 \] \[ 4x^2+10x-13=0 \] \[ \boxed{x=\frac{-5\pm\sqrt{77}}4} \]
