【单选题】What do we mean by a perfect English pronunciation? In one (11) there are as many different kinds of English as there are speakers of it. No two speakers speak in exactly the same (12) We can always h...
【简答题】与等差中项类似,在等比问题中也有等比中项.若 a , G , b 三个数成等比,则把中间那个项 G 叫做 a , b 的 等比中项 . 任何两个数均存在他们的等差中项,且等差中项是唯一的.是否任何两个数都存在等比中项?两个数的等比中项也唯一吗?从等比中项定义可知,两个数 a , b 的等比中项 G 应满足 G 2 = ab . 如数列2,4,8则4是2和8的 等比中项,即 5 与 125 的正等比...