21、4
22、移项1/(x-4)-1/(x-6)=1/(x-8)-1/(x-10)
通分x-6-x+4/(x-4)(x-6)=x-10-x+8/(x-8)(x-10)
化简1/x^2-10x+24=1/x^2-18x+80
所以x^2-10x+24=x^2-18x+80
解得x=7
经检验,x=7是原方程的解.
21、4
22、移项1/(x-4)-1/(x-6)=1/(x-8)-1/(x-10)
通分x-6-x+4/(x-4)(x-6)=x-10-x+8/(x-8)(x-10)
化简1/x^2-10x+24=1/x^2-18x+80
所以x^2-10x+24=x^2-18x+80
解得x=7
经检验,x=7是原方程的解.