题目

计算题1.2.3.12ab2(abc)4÷(－3a2b3c)÷[2(abc)3]4.(a＋b－c)(a－b＋c)  答案： 1.原式＝＝2.原式＝＝ ＝－3.原式＝12a5b6c4÷(－3a2b3c)÷[2a3b3c3] ＝(－4a3b3c3)÷(2a3b3c3) ＝－2 4.原式＝[a＋(b－c)][a－(b－c)] ＝a2－(b－c)2 ＝a2－(b2－2bc＋c2) ＝a2－b2－c2＋2bc 解析:略 -_______ do you read English books?- Three or four times a week.A．How longB．How farC．How muchD．How often