求(1-1/2+1/3-1/4+……+1/99-1/100)/{1/(1+101)+1/(2+102)+……+1/(50150)的值
分子
=(1+1/2+1/3+1/4+……+1/99+1/100)-2*(1/2+1/4+……+1/100)
=1/51+……+1/99+1/100
分母
=1/2 *(1/51+……+1/99+1/100)
原
=1/2
1×2×3×4.99×100×101×102
就是102!
-1+2-3+4-5+6-7+…-99+100-101=?
-1+2-3+4-5+6-7+…-99+100-101
=(-1+2)+(-3+4)+……+(-99+100)-101
= 1×50-101
=50-101
= -51