a) \(27^{64}:81^{20}=3^{192}:3^{80}=3^{112}\)

b) \(\left(\dfrac{1}{8}\right)^{20}:\left(\dfrac{1}{16}\right)^9=\left(\dfrac{1}{2}\right)^{60}:\left(\dfrac{1}{2}\right)^{36}=\left(\dfrac{1}{2}\right)^{24}\)

c) \(\dfrac{1}{3}:\dfrac{1}{5}-\dfrac{1}{6}=\dfrac{5}{3}-\dfrac{1}{6}=\dfrac{10}{6}-\dfrac{1}{6}=\dfrac{9}{6}=\dfrac{3}{2}\)

dễ khủng khíp , động não chút đi

THÌ HÃY LÀ HỘ ĐI

máy tình làm mô ak

a, \(\frac{3}{5}+\frac{-4}{15}=\frac{9}{15}-\frac{4}{15}=\frac{5}{15}=\frac{1}{3}\)

b, \(\frac{-1}{3}+\frac{2}{5}+\frac{2}{15}=\frac{-5}{15}+\frac{6}{15}+\frac{2}{15}=\frac{3}{15}=\frac{1}{5}\)

c, \(\frac{-3}{5}+\frac{7}{21}+\frac{-4}{5}+\frac{7}{5}=\frac{-3}{5}+\frac{1}{3}+\frac{-4}{5}+\frac{7}{5}=\left(\frac{-3}{5}+\frac{-4}{5}+\frac{7}{5}\right)+\frac{1}{3}=\frac{1}{3}\)

d, \(\frac{2}{7}+\frac{1}{9}+\frac{3}{7}+\frac{5}{9}+\frac{-5}{6}=\left(\frac{2}{7}+\frac{3}{7}\right)+\left(\frac{1}{9}+\frac{5}{9}\right)+\frac{-5}{6}=\frac{5}{7}+\frac{6}{9}+\frac{-5}{6}=\frac{90}{126}+\frac{84}{126}+\frac{-105}{126}=\frac{69}{126}=\frac{23}{42}\)

e, \(\frac{-5}{7}+\frac{3}{4}+\frac{-1}{5}+\frac{-2}{7}+\frac{1}{4}=\left(\frac{-5}{7}+\frac{-2}{7}\right)+\left(\frac{3}{4}+\frac{1}{4}\right)+\frac{-1}{5}=\left(-1\right)+1+\frac{-1}{5}=\frac{-1}{5}\)

f, \(\frac{-3}{31}+\frac{-6}{17}+\frac{1}{25}+\frac{-28}{31}+\frac{-1}{17}+\frac{-1}{5}=\left(\frac{-3}{31}+\frac{-28}{31}\right)+\left(\frac{-6}{17}+\frac{-1}{17}\right)+\left(\frac{1}{25}+\frac{-1}{5}\right)=\left(-1\right)+\frac{-7}{17}+\frac{-4}{25}=\frac{-425}{425}+\frac{-175}{425}+\frac{-68}{425}=\frac{-668}{425}\)

Chúc bn học tốt

hi {\___/}

(^__^)

>like>

ngu thế

a) -3/8 <0  ; 4/3 >0   =>  -3/8  < 4/3

b)  11/23 <1  ; 31/8  >1  =>  11/23 <31/8

c)  -5/3  = -15/9  < -14/9

d) 64/85  <  64/81  ; 64/81  <  73/81   =>  64/85  <73/81

Tích cho mk nha !!!~~

\(\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+...+\frac{1}{n.\left(n+3\right)}\)=\(\frac{1}{3}\)(\(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{n}+\frac{1}{n+3}\))=\(\frac{1}{5}-\frac{1}{n+3}=\frac{101}{1540}:\frac{1}{3}=\frac{303}{1540}\)

=>\(\frac{1}{n+3}=\frac{1}{5}-\frac{303}{1540}=\frac{1}{308}\)vậy n= 308+3=311

đơn giản câu trả lời là kêu mod Toán hoặc mạng và 1 cách chứng minh Th1 đề sai thì khỏi

Th2 đè đúng thì đề bảo cm thì chắc chắn nó đúng

nếu thấy dk

Mày ngáo à BIG HERO 6.ko làm hộ người khác thì thôi 

dell thíc đó

\(a)\frac{x}{4}-\frac{3}{7}+\frac{2}{5}=\frac{31}{140}\)

\(\Leftrightarrow\frac{x}{4}-\frac{1}{35}=\frac{31}{140}\)

\(\Leftrightarrow\frac{x}{4}=\frac{1}{4}\Leftrightarrow x=1\)

\(b)\frac{5}{12}+\frac{5}{x}-\frac{1}{8}=\frac{1}{12}\)

\(\Leftrightarrow\frac{5}{x}+\frac{7}{24}=\frac{1}{12}\)

\(\Leftrightarrow\frac{5}{x}=-\frac{5}{24}\Leftrightarrow x=-24\)

ĐẶT \(A=....\)

\(\Rightarrow5A=\frac{5}{1\cdot6}+\frac{5}{6\cdot11}+...+\frac{5}{26\cdot31}=\frac{1}{1}-\frac{1}{6}+\frac{1}{6}-...+\frac{1}{26}-\frac{1}{31}\)

\(\Rightarrow5A=1-\frac{1}{31}=\frac{30}{31}\Rightarrow A=\frac{30}{155}=\frac{6}{31}\)

Đặt A = ...

\(\Rightarrow A=5.\left(\frac{5}{1.6}+\frac{5}{6.11}+...+\frac{5}{26.31}\right)\)

\(\Rightarrow A=5.\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+...+\frac{1}{26}-\frac{1}{31}\right)\)

\(\Rightarrow A=5.\left(1-\frac{1}{31}\right)\)

\(\Rightarrow A=5.\frac{30}{31}\)

\(\Rightarrow A=\frac{150}{31}\)

Đặt \(S=\frac{5^2}{1.6}+\frac{5^2}{6.11}+..+\frac{5^2}{26.31}\)

\(\Leftrightarrow S=\frac{25}{1.6}+\frac{25}{6.11}+..+\frac{25}{26.31}\)

\(\Leftrightarrow\frac{1}{5}S=\frac{5}{1.6}+\frac{5}{6.11}+..+\frac{5}{26.31}\)

\(\Leftrightarrow\frac{1}{5}S=1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+..+\frac{1}{26}-\frac{1}{31}\)

\(\Leftrightarrow\frac{1}{5}S=1-\frac{1}{31}\)

\(\Leftrightarrow\frac{1}{5}S=\frac{30}{31}\)

\(\Leftrightarrow S=\frac{30}{31}\div\frac{1}{5}\)

\(\Leftrightarrow S=\frac{150}{31}\)