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问题: 请问2-2A2-2A3-……-2A18-2A19+2A20=???

请问2-2A2-2A3-……-2A18-2A19+2A20=???

解答:

2-2^2-2^3-2^4-……-2^19+2^20 ???
=2+2^20-(2^2+2^3+2^4+……+2^19)
=2+2^20-(2^2-2*2^19)/(1-2)
=2+2^20+4-2^20
=6.