Ai trả lời được câu này thì mình tíc cho nha !!!

a,\(\left(\dfrac{3}{7}+\dfrac{1}{2}\right)^2\)

\(=\left(\dfrac{13}{14}\right)^2\)

\(=\dfrac{169}{196}\)

b,\(\left(\dfrac{3}{4}-\dfrac{5}{6}\right)^2\)

\(=\left(\dfrac{-1}{12}\right)^2\)

\(=\dfrac{1}{144}\)

c,\(\dfrac{5^4.20^4}{25^5.4^5}\)

\(=\dfrac{100^4}{100^5}\)

\(=\dfrac{1}{100}\)

d,\(\left(\dfrac{-10}{3}\right)^5.\left(\dfrac{-6}{5}\right)^4\)

\(=\left(\dfrac{-10}{3}\right)^4.\left(\dfrac{-6}{5}\right)^4.\left(\dfrac{-10}{3}\right)\)

\(=\left(\dfrac{\left(-10\right)}{3}.\dfrac{\left(-6\right)}{5}\right)^4.\left(\dfrac{-10}{3}\right)\)

\(=4^4.\left(\dfrac{-10}{3}\right)\)

\(=256.\left(\dfrac{-10}{3}\right)\)

\(=\dfrac{-2560}{3}\)

a.\(\left(\frac{3}{7}+\frac{1}{2}\right)^2\)

=\(\left(\frac{6}{14}+\frac{7}{14}\right)^2\)

=\(\left(\frac{13}{14}\right)^2\)

=\(\frac{13^2}{14^2}\)

=\(\frac{169}{196}\)

b.\(\left(\frac{3}{4}-\frac{5}{6}\right)^2\)

=\(\left(\frac{9}{12}-\frac{10}{12}\right)^2\)

=\(\left(\frac{-1}{12}\right)^2\)

=\(\frac{-1^2}{12^2}\)

=\(\frac{1}{144}\).

c.Phần C bn viết lại đề bài đi,mk ko hiểu

d.\(\left(\frac{-10}{3}\right)^5.\left(\frac{-6}{5}\right)^4\)

=\(\frac{-10^5}{3^5}.\left(\frac{-6^4}{5^4}\right)\)

=\(\frac{-100000}{243}.\frac{1296}{625}\)

=\(\frac{-2560}{3}\)

                 Không biết đúng ko nữa

c.\(\frac{5^4.20^4}{25^5.4^5}\)

=\(\frac{25^2.\left(5.4\right)^4}{25^5.4^5}\)

=\(\frac{1.\left(5\right)^4.\left(4\right)^4}{25^3.4^5}\)

=\(\frac{25^2.1}{25^3.4}\)

=\(\frac{1}{25.4}\)

=\(\frac{1}{100}\).

Đề bài phần c là thế này ak Nguyễn Bình Minh:

\(\frac{5^4.20^4}{25^5.4^5}\) ak??

a) \(9.3^3.\frac{1}{81}.3^2=3^2.3^3.\frac{1}{3^4}.3^2=3^7.\frac{1}{3^4}=3^3\)

b) \(4.2^5:\left(2^3.\frac{1}{16}\right)=2^2.2^5:2^3:\frac{1}{16}=2^7:2^3.16=2^4.2^4=2^8\)

c) \(3^2.2^5.\left(\frac{2}{3}\right)^2=3^2.2^5.\frac{2^2}{3^2}=2^5.2^2=2^7\)

d) \(\left(\frac{1}{3}\right)^2.\frac{1}{3}.9^2=\left(\frac{1}{3}\right)^3.\left(3^2\right)^2=\frac{1^3}{3^3}.3^4=1^3.3=3^1\)

a) \(\frac{16}{2^n}=2\)

=> 2.2ⁿ = 16

=> 2¹⁺ⁿ = 2⁴

=> 1 + n = 4

=> n = 4 - 1

=> n = 3

Vậy n = 3

b) \(\frac{\left(-3\right)^n}{81}=-27\)

=> (-3)ⁿ = -27.81

=> (-3)ⁿ = -3³.3⁴

=> (-3)ⁿ = (-3)⁷

=> n = 7

Vậy n = 7

c) 8ⁿ : 2ⁿ = 4

=> (8 : 2)ⁿ = 4

=> 4ⁿ = 4¹

=> n = 1

Vậy n = 1

Ngu xi 

a: \(\Leftrightarrow2^5\ge2^n>2^2\)

=>2<n<=5

hay \(n\in\left\{3;4;5\right\}\)

b: \(\Leftrightarrow3^2\cdot3^3\le3^n\le3^5\)

=>5<=n<=5

=>n=5

no bạn ơi

Ta có công thức tổng quát như sau:

\(A=n^k+n^{k+1}+n^{k+2}+...+n^{k+x}\Rightarrow A=\dfrac{n^{k+x+1}-n^k}{n-1}\)

Áp dụng ta có:

\(A=1+4+4^2+...+4^6=\dfrac{4^7-1}{3}\) 

\(\Rightarrow B-3A=4^7-3\cdot\dfrac{4^7-1}{3}=1\)

______

\(A=2^0+2^1+...+2^{2008}=2^{2009}-1\)

\(\Rightarrow B-A=2^{2009}-2^{2009}+1=1\)

_____

\(A=1+3+3^2+....+3^{2006}=\dfrac{3^{2007}-1}{2}\)

\(\Rightarrow B-2A=3^{2007}-2\cdot\dfrac{3^{2007}-1}{2}=1\)