第94页 - 通城学典课时作业本八年级数学苏科版江苏

C

B

$\frac{2y^2}{9x^2}$

$\frac{81y^{16}}{x^{12}}$

2026

解：原式$= \frac {5c^2\ \mathrm {·} (-3b)}{6ab · a^2c} $

$= \frac {-15bc^2}{6a^3bc} $

$= -\frac {5c}{2a^3}$

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

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

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

解：原式$= \frac {2a^2}{a+4}\ \mathrm {·} \frac {(a-4)(a+4)}{a(a-4)} $

$= \frac {2a^2\ \mathrm {·} (a-4)(a+4)}{(a+4)\ \mathrm {·} a(a-4)} $

$= 2a$

解：原式$= \frac {a+3}{4-a}\ \mathrm {·} \frac {(a-4)^2}{a(a+3)} $

$= \frac {a+3}{-(a-4)}\ \mathrm {·} \frac {(a-4)^2}{a(a+3)} $

$= \frac {(a+3)(a-4)^2}{-(a-4)a(a+3)}$

$= \frac {4 - a}{a}$