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题目内容
用数学归纳法证明1+2+3+…+n
2
=
n
4
+
n
2
2
,则当n=k+1时左端应在n=k的基础上加上( )
A.k
2
+1
B.(k+1)
2
C.
(k+1
)
4
+(k+1
)
2
2
D.(k
2
+1)+(k
2
+2)+(k
2
+3)+…+(k+1)
2