1+1=1 2+1=1 3+4=1 4+9=1 5+7=1 6+18=1 这些等式在什么情况下成立呢?

1/2+1/3+1/4=? 1/2-3/1-4/1= (1-1/2)*(1-1/3)*(1-1/4)*...*(1-1/99)*(1-1/100)= （1-1/2)+(1/2-1/3)+(1/3-1/4)+.+(1/1999-1/2000)= 巧算：(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4+1/5+1/6)-(1+1/2+1/3+1/4+1/5+1/6)*(1/2+1/3+1/4+1/5)(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4+1/5+1/6)-(1+1/2+1/3+1/4+1/5+1/6)*(1/2+1/3+1/4+1/5)===== (1+1/2)*(1-1/2)*(1+1/3)*(1-1/3)*(1+1/4)*(1-1/4)*(1+1/5)*(1-1/5)=? 1+(1/1+2)+(1/1+2+3)+(1/1+2+3+4)+(1/1+2+3+4+...+100)=? 有理数:-1/2+1/3-(-1/9)-1/4= 1/1*3+1/2*4+...+1/9*11=? 1/1*2+1/2*3+1/3*4+...+1/2000*1/2001=1/1*2+1/2*3+1/3*4+...+1/2000*1/20001= (1+1/2)(1+1/3)(1+1/4)...(1+1/2009)= (1-1/2)乘(1-1/3)乘(1-1/4).乘(1-1/2000)=? 1-1/2+1/3-1/4+1/5-1/6+1/7.-1/50=? 2007*(1-1/2)*(1-1/3)*(1-1/4).(1-1/2007)=? 200×(1-1/2)×(1-1/3)×(1-1/4)×……×(1-1/100)=? 1 2 3 4 5=1 1-2/3x=1/4 （x-1/2)/3=1/4