问题24

（A） P=Q–k （B） P=Q+k （C） P=Q （D） P=Q+2K 答复: （A） 说明：

P is sum of odd integers from 1 to 2k

Q is sum of even integers from 1 to 2k

Let k = 5

P is sum of odd integers from 1 to 10
P = 1 + 3 + 5 + 7 + 9

Q is sum of even integers from 1 to 10
Q = 2 + 4 + 6 + 8 + 10

In general, Q can be written as 
Q = (1 + 3 + 5 + 9..... ) + (1 + 1 + .....)
  = P + k

这个问题的小测验