第41页 - 通城学典课时作业本八年级数学人教版南通专版

乘方

乘除

加减

括号里面的

从左往右

D

$m$

$-\frac {1}{a+1}$

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

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

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

$ =\frac {2}{a+1}$

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

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

$=\frac {1}{x}$

$解：原式=\frac {a^2-3\ \mathrm {a}}{a^2+a} ·\frac {a^2-1}{a-3} ·\frac {a+1}{a-1}$

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

$=a+1$

$解：原式=m-1+\frac {2(m-3)}{(m-3)(m+3)} ·\frac {m+3}{2(m+1)}$

$=m-1+\frac {1}{m+1}$

$=\frac {\ \mathrm {m^2}-1}{m+1}+\frac {1}{m+1}$

$=\frac {\ \mathrm {m^2}}{m+1}$