ǰλãҳ > 人教版四年级数学下册第三单元《运算定律》重点知识归纳与易错总结 - 百度文库
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Ԫ㶨ɡص֪ʶ״ܽ
2018 1.ռӷɡɡ˷ɡɺͷɣĸʾ㶨ɡ ѧϰĿ 2.ܽͳ˷õȼ㡣 3.üӷͳ˷㶨ɽһЩ㡣 4.üһЩʵ⡣ 1.̽ӷ˷㶨ɣЩ㶨ɽһЩ㡣 ѧϰص 2.ܹѧ֪ʶʵ⡣ ѧ ýμ ѧ1Ԫص֪ʶ ֪ʶ ӣλúͲ䣬ӷɣa+b=b+aӷɺͽ ӣȰǰӣȰѺӣͲ䡣ͽӷĽɡa+b+c=a+(b+c) Ӧüӷ㶨ɽм һʽУijЩԴճʮ١ǧʱüӷɡӷı˳ʹ㡣 1.ʣ (1)һȥȥĺͣʼӦa-b-c=a-(b+c) (2)У⽻λã䡣a-b-c=a-c-b 2.ӦüʿԽм㡣 ༭
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1.˷ɣˣλã䡣ĸʾΪa˷Ľɡ b=ba 2.˷ɣˣȳǰȳ˺䡣ĸʾΪabc=a(bc) 1.ĺһˣȰֱˣӣdz˷ɡa+bc=ac+bc ˷ɼӦ 2.ˣнӽʮ١ǧԽתʮ١ǧӣһʽó˷ɽм㡣 1.УĻʮٻǧôӦӦóʽмķ a£bc=abcм㡣 ѧ2״֪ʶʾܽ 1ûСı˳ 1ü㷽24+127+476+573 : ȷ: 24+127+476+573 24+127+476+573 =24+476+127+573 =24+476+127+573 =500+700 =24+476+127+573 =1200 =500+700 =1200 㾯ʾ:Ҫ֤ͬʱ24476127573ҪüӷɰС abc=a(bc)м㡣 2.ֽɵǡ뱻ɱϵô༭
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ܲ:üӷĽʱҪעѽϵС 2ȥźδıš 25570-570+340 : ȷ: 5570-570+340 5570-570+340 =5570-570+340 =5570-570-340 =5000+340 =5000-340 =5340 =4660 㾯ʾ:һȥĺ൱ڴӱȥ340Ҫдɼȥ340 ܲ:üʱҪעȥźҪıš 3ûа˳㡣 3500254 : ȷ: 500254 500254 =500100 =204 =5 =80 㾯ʾ:ˡв߱ʱӦմҵ˳㡣 ܲ:ʽʽҪҵ˳㡣 4δֱˡ 420+825 : ȷ: 20+825 20+825 ༭
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=2025+25 =2025+825 =500+25 =500+200 =525 =700 㾯ʾ:ֻ2520ˣû258ˡ ܲ:ó˷ʱֱˡ 5δһת˵ʽм㡣 51521+1578+15 : ȷ: 1521+1578+15 1521+1578+15 =15(21+78)+15 =15(21+78+1) =1599+15 =15100 =1485+15 =1500 =1500 㾯ʾ:15Ҫ151뵽Уż㡣 ܲ:ü㷽ʱһҪϸ۲ʽĽṹص㣬ʱ轫һת˵ʽٽм㡣 ѧ3Ԫϰѵ 1.⣬㡣 ʽУijЩԴճʮٵʱüӷɣӷɣʹ㡣 ༭
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