M is a multiple of 6, the sum of the multiples of 6, from 6 to M, inclusively, is (3)(4)(5). which of the following could be M?
5
12
18
24
30
我真的很晕!!!,(3)(4)(5)是什么意思???
我的理解是(3)(4)(5)是几个质因子
假设M=6K, so sum(from 6 to 6K) = [(6+6K)*K]/2 = 3*K(K+1)
所以K=4
M=24
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