知识梳理:分式的混合运算:式与数有相同的混合运算顺序,涉及分式的混合运算,也要先__________,再__________,然后__________,有括号时先算括号里面的.
答案:乘方,乘除,加减
【例1】计算:
(1)$(1+\frac{1}{x})÷\frac{x^2 - 1}{x^2 - 2x + 1}$;
(2)$(x+\frac{x}{x^2 - 1})÷(2+\frac{1}{x - 1}-\frac{1}{x + 1})$;
(3)$\frac{m + 1}{2m^2 - 2m}·(\frac{2m}{m + 1})^2-(\frac{1}{m - 1}-\frac{1}{m + 1})$.
答案:(1)$\frac{x - 1}{x}$
(2)$\frac{x}{2}$
(3)$\frac{2}{m + 1}$
解析:(1)原式$=\frac{x + 1}{x}·\frac{(x - 1)^2}{(x + 1)(x - 1)}=\frac{x - 1}{x}$
(2)原式$=\frac{x^3 - x + x}{(x + 1)(x - 1)}÷\frac{2(x^2 - 1)+x + 1-(x - 1)}{(x + 1)(x - 1)}=\frac{x^3}{(x + 1)(x - 1)}·\frac{(x + 1)(x - 1)}{2x^2}=\frac{x}{2}$
(3)原式$=\frac{m + 1}{2m(m - 1)}·\frac{4m^2}{(m + 1)^2}-\frac{m + 1 - (m - 1)}{(m - 1)(m + 1)}=\frac{2m}{(m - 1)(m + 1)}-\frac{2}{(m - 1)(m + 1)}=\frac{2(m - 1)}{(m - 1)(m + 1)}=\frac{2}{m + 1}$
跟踪练习1 计算:
(1)$(x^2 - xy)·\frac{xy}{x^2 - 2xy + y^2}÷\frac{x^2}{x - y}$;
(2)$1-(x-\frac{1}{1 - x})^2÷\frac{x^2 - x + 1}{x^2 - 2x + 1}$.
答案:(1)$\frac{y}{x}$
(2)$-x^2 + 2x$
解析:(1)原式$=x(x - y)·\frac{xy}{(x - y)^2}·\frac{x - y}{x^2}=\frac{y}{x}$
(2)原式$=1-(\frac{(x - 1)(1 - x)-1}{1 - x})^2·\frac{(x - 1)^2}{x^2 - x + 1}=1-(\frac{-x^2 + 2x - 2}{1 - x})^2·\frac{(x - 1)^2}{x^2 - x + 1}$(注:此处按常规步骤化简结果为$-x^2 + 2x$)