第57页 - 苏科版数学补充习题八年级上下册答案

$解：最简公分母为2xy$

${\frac {2} {xy}}={\frac {4} {2xy}}$

${\frac {x} {2y}}={\frac {{x}^{2}} {2xy}}$

$解：最简公分母为-20{a}^{2}{b}^{2}$

${\frac {5} {-4a{b}^{2}}}={\frac {25a} {-20{a}^{2}{b}^{2}}}$

${\frac {4} {5{a}^{2}b}}={\frac {-16b} {-20{a}^{2}{b}^{2}}}$

$解：最简公分母为ab(x-y)$

${\frac {x} {a(x-y)}}={\frac {bx} {ab(x-y)}}$

${\frac {y} {b(y-x)}={\frac {-ay} {ab(x-y)}}}$

$解：最简公分母为{(x-y)}^{2}(x+y)$

${\frac {a} {{(y-x)}^{2}}}={\frac {a(x+y)} {{(x-y)}^{2}(x+y)}}$

${\frac {b} {(x-y)(x+y)}}={\frac {b(x-y)} {{(x-y)}^{2}(x+y)}}$

$解：最简公分母为2(a-b)$

${\frac {3a} {2a-2b}}={\frac {3a} {2(a-b)}}$

${\frac {2a} {b-a}}={\frac {-4a} {2(a-b)}}$

$解：最简公分母为(x+1)(x-1)$

${\frac {2} {x-1}}={\frac {2(x+1)} {(x+1)(x-1)}}$

${\frac {3} {x+1}={\frac {3(x-1)} {(x+1)(x-1)}}}$

$解：最简公分母为{(a-2)}^{2}(a+2)$

${\frac {a} {{a}^{2}-4}}={\frac {a} {(a-2)(a+2)}}={\frac {a(a-2)} {{(a-2)}^{2}(a+2)}}$

${\frac {a-1} {a-2}}={\frac {(a-1)(a-2)(a+2)} {{(a-2)}^{2}(a+2)}}$

${\frac {a+2} {{a}^{2}-4a+4}}={\frac {a+2} {{(a-2)}^{2}}}={\frac {{(a+2)}^{2}} {{(a-2)}^{2}(a+2)}}$

$解：最简公分母为(a+1)(a-1)$

${\frac {1} {a+1}}={\frac {a-1} {(a+1)(a-1)}}$

${\frac {3} {1-a}}={\frac {-3(a+1)} {(a+1)(a-1)}}$

${\frac {5} {{a}^{2}-1}}={\frac {5} {(a+1)(a-1)}}$