【答案】
【解析】原式=85.42x56.78-28.65x56.78+56.78x43.23
=56.78x(85.42-28.65+43.23)
=56.78x(85.42=43.23-28.65)
=56.78x(128.65-28.65)
=56.78x100
=5678
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