由数列｛An}是公差为1/2的等差数列可得a1=a2-1/2a3=a4-1/2a5=a6-1/2……a95=a96-1/2a97=a98-1/2a99=a100-1/2已知其前100项和为145即：S100=a1+a2+a3+a4+a5+…+a97+a98+a99+a100=145将上式中的a1,a3,a5…a97,a99用含a...