B

B

\(\text{B.}\dfrac{15}{12}=\dfrac{-10}{-8}\)

\(a,\left(\dfrac{7}{20}+\dfrac{11}{15}-\dfrac{15}{12}\right):\left(\dfrac{11}{20}-\dfrac{26}{45}\right).\)

\(=\left(\dfrac{21}{60}+\dfrac{44}{60}-\dfrac{75}{60}\right):\left(\dfrac{99}{180}-\dfrac{104}{180}\right).\)

\(=\left(\dfrac{65}{60}-\dfrac{75}{60}\right):\left(-\dfrac{5}{180}\right).\)

\(=-\dfrac{10}{60}:\left(-\dfrac{5}{180}\right).\)

\(=-\dfrac{1}{6}:\left(-\dfrac{1}{36}\right).\)

\(=-\dfrac{1}{6}.\left(-36\right).\)

\(=\dfrac{-1.\left(-36\right)}{6}=\dfrac{36}{6}=6.\)

Vậy......

\(b,\dfrac{5-\dfrac{5}{3}+\dfrac{5}{9}-\dfrac{5}{27}}{8-\dfrac{8}{3}+\dfrac{8}{9}-\dfrac{8}{27}}:\dfrac{15-\dfrac{15}{11}+\dfrac{15}{121}}{16-\dfrac{16}{11}+\dfrac{16}{121}}.\)

\(=\dfrac{5\left(1-\dfrac{1}{3}+\dfrac{1}{9}-\dfrac{1}{27}\right)}{8\left(1-\dfrac{1}{3}+\dfrac{1}{9}-\dfrac{1}{27}\right)}:\dfrac{15\left(1-\dfrac{1}{11}+\dfrac{1}{121}\right)}{16\left(1-\dfrac{1}{11}+\dfrac{1}{121}\right)}.\)

\(=\dfrac{5}{8}:\dfrac{15}{16}.\)

\(=\dfrac{5}{8}.\dfrac{16}{15}=\dfrac{5.16}{8.15}=\dfrac{1.2}{1.3}=\dfrac{2}{3}.\)

Vậy......

c, (làm tương tự câu b).

~ Học tốt!!! ~

Ta có: \(\frac{8^{10}.15^{16}}{12^{15}.25^8}=\frac{\left(2^3\right)^{10}.\left(3.5\right)^{16}}{\left(2.2.3\right)^{15}.\left(5^2\right)^8}\)

                              \(=\frac{2^{30}.3^{16}.5^{16}}{2^{15}.2^{15}.3^{15}.5^{16}}\)

                             \(=\frac{2^{30}.3^{16}.5^{16}}{2^{30}.3^{15}.5^{16}}\)

                              \(=\frac{3^{16}}{3^{15}}\)

                             \(=3\)

Học tốt nha^^

ra 24 bạn tách các số ra và rút gọn

\(a.\)

\(\dfrac{3}{16}:\dfrac{?}{8}=\dfrac{3}{4}\)

\(\Leftrightarrow\dfrac{3}{16}\cdot\dfrac{8}{?}=\dfrac{3}{4}\)

\(\Leftrightarrow\dfrac{3}{2?}=\dfrac{3}{4}\)

\(\Leftrightarrow?=2\)

\(b.\)

\(\dfrac{1}{25}:-\dfrac{3}{?}=-\dfrac{1}{15}\)

\(\Leftrightarrow\dfrac{1}{25}\cdot\dfrac{-?}{3}=-\dfrac{1}{15}\)

\(\Leftrightarrow\dfrac{-?}{75}=-\dfrac{1}{15}\)

\(\Leftrightarrow?=\dfrac{75}{15}=5\)

\(c.\)

\(\dfrac{?}{12}:-\dfrac{4}{9}=-\dfrac{3}{16}\)

\(\Leftrightarrow\dfrac{?}{12}\cdot\dfrac{-9}{4}=-\dfrac{3}{16}\)

\(\Leftrightarrow\dfrac{-3?}{16}=-\dfrac{3}{16}\)

\(\Leftrightarrow?=1\)

Mk gọi ? = x nha

a) \(\dfrac{3}{16}:\dfrac{x}{8}=\dfrac{3}{4}\)  

             \(\dfrac{x}{8}=\dfrac{3}{16}:\dfrac{3}{4}\) 

             \(\dfrac{x}{8}=\dfrac{1}{4}\)

⇒\(x=\dfrac{1.8}{4}=2\) 

b) \(\dfrac{1}{25}:\dfrac{-3}{x}=\dfrac{-1}{15}\) 

             \(\dfrac{-3}{x}=\dfrac{1}{25}:\dfrac{-1}{15}\) 

             \(\dfrac{-3}{x}=\dfrac{-3}{5}\) 

⇒x=5

c) \(\dfrac{x}{12}:\dfrac{-4}{9}=\dfrac{-3}{16}\) 

            \(\dfrac{x}{12}=\dfrac{-3}{16}.\dfrac{-4}{9}\) 

            \(\dfrac{x}{12}=\dfrac{1}{12}\) 

⇒x=1

Cần kết quả thôi hay cả cách làm ạ?

\(\dfrac{8^{10^{^{ }}}.15^{16}}{12^{15}.25^8}\)=\(\dfrac{2^{30}.5^{16}.3^{16}}{2^{30}.3^{15}.5^{16}}\)=3

\(\dfrac{8^{10}.15^{16}}{12^{15}.25^8}\)

\(=\dfrac{\left(2.2.2\right)^{10}.\left(3.5\right)^{16}}{\left(3.2.2\right)^{15}.\left(5.5\right)^8}\)

\(=\dfrac{2^{10}.2^{10}.2^{10}.3^{16}.5^{16}}{3^{15}.2^{15}.2^{15}.5^8.5^8}\)

\(=\dfrac{3}{1}\)

\(=3\)

\(\dfrac{15}{25};\dfrac{16}{20};\dfrac{12}{10}\)

15/25 ; 16/20 ; 12/10

\(\dfrac{15}{25};\dfrac{16}{20};\dfrac{12}{10}\)

ta rút gọn là xong

= -3.5.8 phần 2.4.2. -5 .5,ta gạch số giống nhau và nhân số còn lại là xong