(x-2)(2x-5)-2(x-1)(x+1)=3(2x²-5x-4x+10)-2(x²-1)=32x²-9x+10-2x²+2=3-9x+10+2=3-9x=-9x=1
左边展开为2x^2-9x+10-(2x^2-2)=-9x+2=3所以 x=-1
