第45页

信息发布者:
解:原式$= (-36)×\dfrac{1}{4} - (-36)×\dfrac{5}{9} + (-36)×\dfrac{1}{12}$
$= -9 + 20 - 3$
$= 8$
解:原式$= 25×[\dfrac{3}{4} + \dfrac{1}{2} + (-\dfrac{1}{4})]$
$= 25×1$
$= 25$
解:
因为
$(\dfrac{1}{6}-\dfrac{2}{7}+\dfrac{2}{3}-\dfrac{3}{14})÷(-\dfrac{1}{42})=(\dfrac{1}{6}-\dfrac{2}{7}+\dfrac{2}{3}-\dfrac{3}{14})×(-42)$
$=\dfrac{1}{6}×(-42)-\dfrac{2}{7}×(-42)+\dfrac{2}{3}×(-42)-\dfrac{3}{14}×(-42)$
$=-7 + 12 - 28 + 9$
$=-14$
所以$(-\dfrac{1}{42})÷(\dfrac{1}{6}-\dfrac{2}{7}+\dfrac{2}{3}-\dfrac{3}{14})=-\dfrac{1}{14}$
C
A