如题所述
25×27×（25×1/26+26×1/27）
=25×27×（25/26+26/27）
=25×27×25/26+25×27×26/27
=25×（26+1）×25/26+650
=25×（26×25/26+1×25/26）+650
=25×（25+25/26）+650
=25×25+25×25/26+650
=625+650+（26-1）×25/26
=1275+26×25/26-1×25/26
=1275+25-25/26
=1300-25/26
=1299又1/26
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