cố lên ARMY

BTS ra album mới rồi^_^ mừng quá!

(=)(1/64)^x=(-1/8)^2^7

(=)(1/64)^x=(1/64)^7

=>x=7

\(\left(\frac{1}{64}\right)^x=\left(-\frac{1}{8}\right)^{14}\)

\(=\left(\frac{1}{64}\right)^x=\left(\frac{1}{64}\right)^7\)

\(\Rightarrow x=7\)

Vậy x = 7 

\(M=\frac{5}{2\cdot7}+\frac{4}{7\cdot11}+\frac{3}{11\cdot14}+\frac{1}{14\cdot15}+\frac{13}{15\cdot28}\)

\(M=\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{15}-\frac{1}{28}\)

\(M=\frac{1}{2}-\frac{1}{28}\)

\(M=\frac{13}{28}\)

Ta có :

\(2^2:1^2=4\)

\(4^2:2^2=4\)

.....

\(20^2:10^2=4\)

\(\Rightarrow A=4\cdot1^2+4\cdot2^2+...+4\cdot10^2\)

\(\Rightarrow A=4\cdot\left(1^1+2^2+...+10^2\right)\)

\(\Rightarrow A=4\cdot385\)

\(\Rightarrow A=1432\)

a,(=)\(3^{x+1}.\left(3+4\right)=7.3^6\)

(=)\(3^{x+1}=3^6\)

=>x+1=6(=)x=5

b

\(a,\frac{16}{2^n}=2\)

\(\Rightarrow\frac{16}{2^n}=\frac{2}{1}\)

\(\Rightarrow2^n.2=16\)

\(\Rightarrow4^n=4^2\)

\(\Rightarrow n=2\)

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

\(\Rightarrow\left(-3\right)^n=81.\left(-27\right)\)

\(\Rightarrow\left(-3\right)^n=-2187\)

\(\Rightarrow\left(-3\right)^n=\left(-3\right)^7\)

\(\Rightarrow n=7\)

16/2^n=2 => 2^n .2 =16 => 2^n=8=2^3=>n=3

a, ( 1 + 2/3 -1/4 ) . ( 4/5 - 3/4 )² = 17/12 . (1/20)²

                                                = 17/12 . 1/400

                                                = 17/4800

b, 2 : ( 1/2 - 2/3 )³ = 2 : (-1/6)³

                             = 2 : (-1/216)

                             = -432