Đáp án:
Giải thích các bước giải:
e) $\eqalign{ & (\frac{x}{y} + \frac{y}{x}):(\frac{{x - y}}{{x + y}} + \frac{{x + y}}{{x - y}}) \cr & = \frac{{{x^2} + {y^2}}}{{xy}}:\frac{{{{(x - y)}^2} + {{(x + y)}^2}}}{{(x + y)(x - y)}} \cr & = \frac{{{x^2} + {y^2}}}{{xy}}.\frac{{(x + y)(x - y)}}{{{x^2} - 2xy + {y^2} + {x^2} + 2xy + {y^2}}} \cr & = \frac{{{x^2} + {y^2}}}{{xy}}.\frac{{(x + y)(x - y)}}{{2({x^2} + {y^2})}} \cr & = \frac{{(x + y)(x - y)}}{{2xy}} \cr} $
j) $\eqalign{ & (\frac{{a - x}}{a} + \frac{x}{{a - x}}):(\frac{{a + x}}{a} - \frac{x}{{a + x}}) \cr & = \frac{{{{(a - x)}^2} + ax}}{{a(a - x)}}:\frac{{{{(a + x)}^2} - ax}}{{a(a + x)}} \cr & = \frac{{{a^2} - 2ax + {x^2} + ax}}{{a(a - x)}}.\frac{{a(a + x)}}{{{a^2} + 2ax + {x^2} - ax}} \cr & = \frac{{(a + x)({a^2} - ax + {x^2})}}{{(a - x)({a^2} + ax + {x^2})}} \cr} $
