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n为正整数,则(-1)2n=________,(-1)2n+1=________.
n为正整数,则(-1)2n=___,(-1) 2n+1=______.
若n为正整数,且x2n=7,则(3x3n)2-4(x2)2n的值为
[ ]
A.833
B.2891
C.3283
D.1225