199^2+(199乘200)^2+200^2=(199乘200+1）^2的值是多？

数不清?1+1/1*2+1/2*

1+1/(1*2)+1/(2*3)+1/(3*4)+。。。。。。+1/(199*200) =1+(2-1)/(1*2)+(3-2/(2*3)+(4-3)/(3*4)+。。。。。。+(200-199)/(199*200) =1+(1-1/2)+(1/2-1/3)+(1/3-1/4)+。 。。。。。+(1/199-1/200) =1+(1-1/200) =399/200。

  1+1/(1*2)+1/(2*3)+1/(3*4)+。。。。。。+1/(199*200) =1+(2-1)/(1*2)+(3-2/(2*3)+(4-3)/(3*4)+。。。。。。+(200-199)/(199*200) =1+(1-1/2)+(1/2-1/3)+(1/3-1/4)+。
  。。。。。+(1/199-1/200) =1+(1-1/200) =399/200。收起