第95页 - 通城学典课时作业本八年级数学苏科版江苏专版

$ \begin{aligned}解：原式&=\frac {4m+5+(m-1)(m+1)}{m+1}÷\frac {m+2}{m+1} \\ &=\frac {4m+5+\ \mathrm {m^2}-1}{m+1}×\frac {m+1}{m+2} \\ &=\frac {(m+2)^2}{m+1}×\frac {m+1}{m+2} \\ &=m+2 \\ \end{aligned}$

$ \begin{aligned}解：原式&=\frac {a+b-b}{(a+b)(a-b)}×\frac {(a-b)^2}{a(a-b)} \\ &=\frac 1{a+b} \\ \end{aligned}$

$解：原式=x+3.$

$当x=-\frac{7}{2}时，原式=-\frac{1}{2}$

D

$-\frac{1}{2}$

$ \begin{aligned}解：3-x-1&=x-4 \\ x&=3 \\ \end{aligned}$

$检验：当x=3时，x-4≠0$

$∴x=3是方程的解$

$ \begin{aligned}解：x(x+2)-(x-1)(x+2)&=3 \\ x^2+2x-x^2-2x+x+2&=3 \\ x&=1 \\ \end{aligned}$

$检验：当x=1时，(x-1)(x+2)=0$

$∴x=1是增根，原方程无解$

D