1/(1+√2) = √2-1 (上下同时乘以 √2-1 )
1/(√2+√3)= √3-√2 (上下同时乘以√3-√2 )
1/(√3+√4)= √4-√3 (上下同时乘以√4-√3 )
.
.
.
1/(√99+√100)= √100-√99 (上下同时乘以√100-√99 )
所以
1/(1+√2) + 1/(√2+√3) + 1/(√3+√4)+...+1/(√99+√100)
=(√2-1)+(√3-√2)+ (√4-√3)+...+(√100-√99)
=√100 - 1 (中间全约掉了)
=10-1
=9