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電子課本網(wǎng) 第72頁

第72頁

信息發(fā)布者:
解:原式??$=\frac {y(y-x)+xy}{y2-x2}$??
??$ =\frac {y2}{y2-x2}$??
解:原式??$=\frac {(a+5)(a-4)}{5(a-4)2}+\frac {25}{5(a-4)2}$??
??$ =\frac {a2+a+5}{5(a-4)2}$??
解:原式??$=\frac {2(x-3)}{x2-9}+\frac {2(x+3)}{x2-9}+\frac {2x+18}{x2-9}$??
??$ =\frac {2x-6+2x+6+2x+18}{x2-9}$??
??$ =\frac {6}{x-3}$??
因為分式的值為整數(shù)
所以??$x-3=±1,$????$±2,$????$±3,$????$±6$??
因為分式有意義
所以??$x≠3$??且??$x≠-3$??
所以??$x=0,$????$1,$????$2,$????$4,$????$5,$????$6,$????$9$??
和為??$27$??

解:??$\frac {1}{a}-\frac {1}=\frac {b-a}{ab}=\frac {1}{2}$??
原式??$=-\frac {ab}{b-a}=-2$??
$ 解:原式??$
$=\frac{9a^2(b^2)^2}{4(c^2)^2(d^3)^2}$
$=\frac {9a^2b^4}{4c^4d^6}$??
$解:原式$
??$=\frac{8(a^2)^3b^3}{(-c^3)^3}$
$=-\frac {8a^6b^3}{c^9}$$??$