化简1.9x-9/4-4x 2.x^2-1/x^2+x-2 3.x^2-4x+4/2x-4 4.3x^2-9x-12/x^2+2x+1 5.x^2-7x+12/-x^2+9x-20 急
问题描述：
化简1.9x-9/4-4x 2.x^2-1/x^2+x-2 3.x^2-4x+4/2x-4 4.3x^2-9x-12/x^2+2x+1 5.x^2-7x+12/-x^2+9x-20 急
6.xy-x-y+1/y^2-2y+1
答
1.9x-9/4-4x =9(x-1)/4(1-x)=-9/42.x^2-1/x^2+x-2=(x+1)(x-1)/(x-1)(x+2)=(x+1)/(x+2) 3.x^2-4x+4/2x-4 =(x-2)²/2(x-2)=(x-2)/24.3x^2-9x-12/x^2+2x+1=3(x-4)(x+1)/(x+1)²=3(x-4)/(x+1) 5.x^2-7x+12/-x^2+...