A+2A+3A+.+49A+50A+50B+49B+.+2B+B
问题描述:
A+2A+3A+.+49A+50A+50B+49B+.+2B+B
答
A+2A+3A+.+49A+50A+50B+49B+.+2B+B
= [(1+50)*50/2] *(A+B)
= 1275(A+B)