> 数学 >
M=
1
3
a(a+1)(a+2),N=
1
3
a(a−1)(a+1)
,那么M-N等于(  )
A. a2+a
B. (a+1)(a+2)
C.
1
3
a2+
1
3
a

D.
1
3
(a+1)(a+2)
人气:246 ℃ 时间:2020-10-01 23:22:59
解答
M-N=
1
3
a(a+1)(a+2)-
1
3
a(a-1)(a+1)
=
1
3
a(a+1)[a+2-(a-1)]
=a2+a.
故选:A.
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