设(1-1/2-1/3-1/4-1/5)为a,(1/2+1/3+1/4+1/5)为b,代入得转化为a(b+1/6)-(a-1/6)b,得到ab+1/6a-ab+1/6b,化简为1/6(a+b),再重新代入,解得1/6(1-1/2-1/3-1/4-1/5+1/2+1/3+1/4+1/5)=1/6*1=1/6
答:
设a=1/2+1/3+1/4+1/5+1/6
原式
=(l-1/2-1/3-1/4-1/5)(1/2+1/3+1/4+1/5+1/6)一(l-1/2-1/3-1/4-1/5-1/6)(1/2+1/3+1/4+1/5)
=[1-(a-1/6)]*a-(1-a)(a-1/6)
=(7/6-a)a+(a-1)(a-1/6)
=7a/6-a^2+a^2-7a/6+1/6
=1/6