Question

Tìm n, biết

a. \(\left(\dfrac{1}{2}\right)^{2n-1}=\dfrac{1}{8}\)

b. \(\left(\dfrac{7}{5}\right)^n=\dfrac{343}{125}\)

Answer 1

a) \(\left(\dfrac{1}{2}\right)^{2n-1}=\dfrac{1}{8}\)

\(\Rightarrow\left(\dfrac{1}{2}\right)^{2n-1}=\left(\dfrac{1}{2}\right)^3\)

\(\Rightarrow2n-1=3\)

\(\Rightarrow2n=4\)

\(\Rightarrow n=2\)

Answer 2

a) \(\left(\dfrac{1}{2}\right)^{2n-1}=\dfrac{1}{8}\)

\(\Rightarrow2^{-\left(2n-1\right)}=2^{-3}\)

\(\Rightarrow2^{-2n+1}=2^{-3}\)

\(\Rightarrow-2n+1=-3\)

\(\Rightarrow-2n=-4\)

\(\Rightarrow n=-2\)

Vậy ...

b) \(\left(\dfrac{7}{5}\right)^n=\dfrac{343}{125}\)

\(\Rightarrow\left(\dfrac{7}{5}\right)^n=\left(\dfrac{7}{5}\right)^3\)

\(\Rightarrow n=3\)

Vậy ....

Answer 3

a. )\(\left(\dfrac{1}{2}\right)^{2n-1}\)=\(\dfrac{1}{8}\)

=> 2n-1=3

=>2n=3+1

=>2n=4

=>n=4:2=2

Answer 4

b. \(\left(\dfrac{7}{5}\right)\)^n = \(\left(\dfrac{343}{125}\right)\)

=> n= 3

Answer 5

a. \(\left(\dfrac{1}{2}\right)^{2n-1}=\dfrac{1}{8}\)

\(\Rightarrow\left(\dfrac{1}{2}\right)^{2n-1}=\left(\dfrac{1}{2}\right)^3\)

\(\Rightarrow2n-1=3\)

\(\Rightarrow2n=3+1=4\)

\(\Rightarrow n=4:2=2\)

Vậy....

b. \(\left(\dfrac{7}{5}\right)^n=\dfrac{344}{125}\)

\(\Rightarrow\left(\dfrac{7}{5}\right)^n=\left(\dfrac{7}{3}\right)^3\)

\(\Rightarrow n=3\)

Vậy..........

Answer 6

Kq phần a mình bj nhầm nhé , là 2 mới đúg

Answer 7

Lưu Hạ Vi sai kết quả câu a) mà vẫn được tick ;

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