【正文】
c + c 3a 52 2c ab 返回 數(shù)和字母相乘,在省略乘號(hào)時(shí),要把數(shù)字寫在字母的前面。 . ( 1)數(shù)和字母相乘,在省略乘號(hào)時(shí),要把數(shù)字寫在字母的前面。 ( 4) a( a≠0)的倒數(shù)是__, a的相反數(shù)是__ 。 a + b = b + a (a + b) +c = a +(b + c) a b = b a (a b) c = a (b c) (a + b) c = a c+b c a a a b a h a h a h b S = a a S = a b S = a h S = a