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第74頁

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解：原式?$=4x2y÷\frac {4x2}{y2}$?
?$ =4x2y×\frac {y2}{4x2}$?
?$ =y3$?
解：原式?$=\frac {3(a-b)}{10ab}×\frac {15a2b2}{(a+b)(a-b)}$?
?$ =\frac {9ab}{2(a+b)}$?
解：原式?$=\frac {(x-2y)(x+2y)}{(x+y)2}×\frac {x(x+y)}{x+2y}$?
?$ =\frac {x(x-2y)}{x+y}$?
解：原式?$=\frac {2(x-3)}{(x-2)2}×\frac {1}{x+3}×\frac {(x+3)(x-2)}{3-x}$?
?$ =-\frac {2}{x-2}$?
解：原式?$=\frac {x+3y}{(x+2y)(x-2y)}×\frac {x+2y}{(x+3y)2}$?
?$ =\frac {1}{(x-2y)(x+3y)}$?
因為?$x2+y2-4x+6y+13=0$?
所以?$(x-2)2+(y+3)2=0$?
所以?$x=2，$??$y=-3$?
所以原式?$=\frac {1}{(2+6)×(2-9)}=-\frac {1}{56}$?


解：原式?$=[\frac {x+2}{x(x-2)}-\frac {x-1}{(x-2)2}]×\frac {x}{x-4}$?
?$ =\frac {x-4}{x(x-2)2}×\frac {x}{x-4}$?
?$ =\frac {1}{(x-2)2}$

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