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第63頁

信息發(fā)布者：

$?? -a^2b-a b^2??$

C

$解：原式??=\frac {x-1}x÷\frac {x-1}x??$

$?? =1??$

$解：原式??=xy^2 ·\frac {(x+1)(x-1)}{x+1} ·\frac {xy^2}{x-1}??$

$?? =x^2y^4??$

解：原式??$=\frac {3-m}{2(m-2)}÷\frac {\ \mathrm {m^2}-4-5}{m-2}$??

??$ =\frac {3-m}{2(m-2)} ·\frac {m-2}{(m+3)(m-3)}$??

??$ = -\frac 1{2(m+3)}$??

$解：原式??=1-\frac {a-b}{a+2b} ·\frac {(a+2b)^2}{(a+b)(a-b)}??$

$?? =1-\frac {a+2b}{a+b}??$

$?? =-\frac b{a+b}??$

$解：原式??=a+\frac 1{2a-1}-\frac {2a+1}{2a}÷\frac {2a-1}a ??$

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

$?? =\frac {4a^2-2a+2-2a-1}{2(2a-1)}??$

$?? =\frac {2a-1}2??$

$?? =a-\frac 12??$

$當??a=\frac 58??時，原式??=\frac 58-\frac 12=\frac 18??$

$解：??x^2+1=5x??$

$兩邊同時除??x，??得??x+\frac 1x=5??$

$ 則有??x^2+\frac 1{x^2}=(x+\frac 1x)^2-2=5^2-2=23??$

$ ∴??(x-\frac 1x)^2=x^2+\frac 1{x^2}-2=23-2=21??$

$ ∴??x-\frac 1x=±\sqrt {21}??$

解：原式??$=\frac ab+\frac ac+\frac bc+\frac ba+\frac ca+\frac cb$??

??$ =\frac {a+c}b+\frac {a+b}c+\frac {b+c}a$??

∵??$a+b+c=0$??

∴??$a+c=-b，$????$a+b=-c，$????$b+c=-a$??

∴原式??$=-1-1-1=-3$??

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