NK-NK+- is equal to (1+2+3+...+201)-(1+2+3 ...+2012) =-2065438.
k = 1k = 1 20 1 1
20 12 20 12*20 1 1
Calculating:-equals-equals 20 1 1. The original formula of this formula is: -20 1 1+2065438+.
20 1 1 20 1 1
Nk should be "∑" symbol.
Hope to adopt, this is the correct answer.