运用乘法运算定律,怎么比较234乘456和235乘455的大小
234×456
=234×(455+1)
=234×455+234×1
=(235-1)×455+234
=235×455-1×455+234
=235×455-455+234
=235×455-(455-234)
=235×455-221
所以234×456<235×455
本题:
∵234*456-235*455=(235-1)*456-235*455
=235*456-456-235*455
=235*(456-455)-456
=235-456
=-221<0
∴234*456<235*455
235*455-234*456
=(234+1)*455-234*(455+1)
=455-234
=221>0
即235*455-234*456>0
235*455>234*456
234×456
=(235-1)×(455+1)
=235×455-455+235-1
234×456-235×455
=235×455-455+235-1-235×455
=235-456
=-221
所以:234×456<235×455
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