Đáp án:
a.$A=-\dfrac{11}4$
b.$A=\dfrac{-2}{3}$
c.$A=-\dfrac{119}{48}$
Giải thích các bước giải:
a.Nếu $\dfrac mn=\dfrac{-5}6$
$\to A=\dfrac{-2}{3}-(\dfrac{-5}6+\dfrac{-5}{2})\cdot\dfrac{-5}8$
$\to A=-\dfrac23-(-\dfrac{10}{3})\cdot\dfrac{-5}8$
$\to A=-\dfrac23-\dfrac{25}{12}$
$\to A=-\dfrac{11}4$
b.Nếu $\dfrac mn=\dfrac52$
$\to A=\dfrac{-2}{3}-(\dfrac52+\dfrac{-5}{2})\cdot\dfrac{-5}8$
$\to A=\dfrac{-2}{3}-0\cdot\dfrac{-5}8$
$\to A=\dfrac{-2}{3}-0$
$\to A=\dfrac{-2}{3}$
c.Nếu $\dfrac mn=\dfrac2{-5}$
$\to A=\dfrac{-2}{3}-(\dfrac2{-5}+\dfrac{-5}{2})\cdot\dfrac{-5}8$
$\to A=\dfrac{-2}{3}-(-\dfrac{29}{10})\cdot\dfrac{-5}8$
$\to A=\dfrac{-2}3-\dfrac{29}{16}$
$\to A=-\dfrac{119}{48}$