(3x-2x^2)(3-2x-x^2)除以(x^2+x)(2x^2-5x+3)
=[x(3-2x)(3+x)(1-x)]除以[x(x+1)(x-1)(2x-3)]
=[x(2x-3)(3+x)(x-1)]除以[x(x+1)(x-1)(2x-3)]
=(x+3)/(x+1)