【正文】
乘法分配律: (a+b) c = a c + b c a c + b c = (a+b) c (a- b) c = a c - b c a c - b c = (a- b) c 用簡(jiǎn)便方法計(jì)算: 課本第 46頁第 2題; 47頁第 1題。 ( 20+4) 25 =20 25+4 25 =500+100 =600 35 37+65 37 =( 35+65) 37 =100 37 =3700 99 11 329 101 =( 1001) 11 =100 111 11 =110011 =1089 =329 ( 100+1) =329 100+329 1 =32900+329 =33229 32 ( 200+3) 38 29+38 =32 200+32 3 =6400+96 =6496