x(x-1)分之一+x(x+1)分之一+????????+(x+9)(x+10)分之一=12分之11 怎么算？

x(x-1)分之一+x(x+1)分之一+????????+(x+9)(x+10)分之一 =1/(x-1)-1/x+1/x-1/(x+1)+.........1/(x+9)-1/(x+10) =1/(x-1)-1/(x+10) =11/12 12(x+10-x+1)=11(x-1)(x+10) 12*11=11(x-1)(x+10) 12=(x-1)(x+10) x^2+9x-22=0 (x+11)(x-2)=0