\(\frac{6^5.35^7}{14^7.15^5}=\frac{2^5.3^5.5^7.7^7}{2^7.7^7.3^5.5^5}=\frac{5^2}{2^2}=\frac{25}{4}\)

a)\(\frac{1}{n}-\frac{1}{n+1}=\frac{n+1}{n\left(n+1\right)}-\frac{n}{n\left(n-1\right)}=\frac{n+1-n}{n\left(n+1\right)}=\frac{1}{n\left(n+1\right)}\)

\(\Rightarrow\frac{1}{n\left(n+1\right)}=\frac{1}{n}.\frac{1}{n+1}\)

b) \(C=\frac{1}{2}.\frac{1}{3}+\frac{1}{3}.\frac{1}{4}+\frac{1}{4}.\frac{1}{5}+\frac{1}{5}.\frac{1}{6}+\frac{1}{6}.\frac{1}{7}+\frac{1}{7}.\frac{1}{8}\)

\(=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}\)

\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)

\(=\frac{1}{2}+0+0+0+0+0-\frac{1}{8}\)

\(=\frac{1}{2}-\frac{1}{8}=\frac{4}{8}-\frac{1}{8}=\frac{4-1}{8}=\frac{3}{8}\)

a: \(=\dfrac{-4\cdot13\cdot9\cdot5}{3\cdot4\cdot5\cdot2\cdot13}=\dfrac{3}{2}\)

b: \(=\dfrac{1}{2}\cdot\dfrac{1}{3}\cdot5=\dfrac{5}{6}\)

Ta có 29/-66>30/-66

→ 26/-66 > -5/11

a) -5/11 = -30/11 

-30/11 < 39/-66

Vậy -5/11 < 29/-66

a,<

b,=

c,<

d,=

\(\frac{2}{-5}=\frac{-24}{60}\)

\(\frac{3}{-4}=\frac{-45}{60}\)

\(\frac{6}{-24}=\frac{-1}{4}=\frac{-15}{60}\)

\(-\frac{8}{80}=\frac{-1}{10}=\frac{-6}{60}\)

\(\frac{7}{-14}=-\frac{1}{2}=\frac{-30}{60}\)

\(\frac{2}{-5}=\frac{-2}{5}=\frac{-24}{60}\)
tương tự 
 

\(\frac{2}{-5}=\frac{-2}{5}=\frac{-2.12}{5.12}=\frac{-24}{60}\)

\(\frac{3}{-4}=\frac{-3}{4}=\frac{-3.15}{4.15}=\frac{-45}{60}\)

\(\frac{6}{-24}=\frac{1}{-4}=\frac{-1}{4}=\frac{-1.15}{4.15}=\frac{-15}{60}\)

\(\frac{-8}{80}=\frac{-1}{10}=\frac{-1.6}{10.6}=\frac{-1}{60}\)

\(\frac{7}{-14}=\frac{1}{-2}=\frac{-1}{2}=\frac{-1.30}{2.30}=\frac{-30}{60}\)

\(\frac{75}{2}\)

\(=\frac{\left(2.3\right)^6.\left(5.7\right)^7}{\left(2.7\right)^4.\left(3.5\right)^5}=\frac{2^6.3^6.5^7.7^7}{2^4.7^4.3^5.5^5}=\frac{2^2.3.5^2.7^3}{1.1.1.1}=\left(4.25\right).3.7^3=100.3.343=102900\)

kiều bích huyền ghi sai đề làm bậy luôn