4·7×2·8＋2·5×2·8＋7·2×7·2
=2.8×（4.7+2.5）＋7·2×7·2
=2.8×7·2＋7·2×7·2
=7.2x（2.8+7.2）
=7.2x10
=72
4·7×2·8＋2·5×2·8＋7·2×7·2﹙简便运算,用递等式计算﹚
4·7×2·8＋2·5×2·8＋7·2×7·2﹙简便运算,用递等式计算﹚
数学人气：550 ℃时间：2019-10-11 10:08:56
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