Đáp án:
$e) 7\\
f) \dfrac{-1}{7}\\
g) \dfrac{17}{21}\\
h) \dfrac{1}{4}\\
f) \dfrac{1}{5}\\
k) \dfrac{1}{2}\\
l)\dfrac{-4}{3}$
Giải thích các bước giải:
$e) \dfrac{13.9-13.2}{25-12}=\dfrac{13(9-2)}{13}=7\\
f) \dfrac{(-7).3-4.(-6)}{(-5).3-2.3}=\dfrac{-3(7-8)}{-3(5+2)}=\dfrac{-1}{7}\\$
$g) \dfrac{(-17).13+17.2}{-11.2-11.19}=\dfrac{17(-13+2)}{-11(2+19)}=\dfrac{17.(-11)}{(-11).21}=\dfrac{17}{21}\\$
$h) \dfrac{5.5^2}{9.10^2-4.10^2}=\dfrac{5^3}{10^2(9-4)}=\dfrac{5^2}{10^2}=(\dfrac{5}{10})^2=\dfrac{1}{2}^2=\dfrac{1}{4}\\$
$f)
\dfrac{14}{26}.\dfrac{13}{35}=\dfrac{7.2.13}{2.13.7.5}=\dfrac{1}{5}\\$
$k) \dfrac{32}{12}.\dfrac{9}{24}.\dfrac{11}{22}=\dfrac{8.4.3^2.11}{3.4.8.3.2.11}=\dfrac{1}{2}\\$
$l) \dfrac{\dfrac{4}{11}-\dfrac{12}{31}+\dfrac{16}{59}}{-\dfrac{3}{11}+\dfrac{9}{31}-\dfrac{12}{59}}\\
=\dfrac{4}{3}.\dfrac{3.\left(\dfrac{4}{11}-\dfrac{12}{31}+\dfrac{16}{59}\right)}{(-4).\left (-\dfrac{3}{11}+\dfrac{9}{31}-\dfrac{12}{59} \right )}\\$
$=\dfrac{-4}{3}.\dfrac{\dfrac{12}{11}-\dfrac{36}{31}+\dfrac{48}{59}}{\dfrac{12}{11}-\dfrac{36}{31}+\dfrac{48}{59}}\\$
$=\dfrac{-4}{3}$
