Question

a) -512/343=(-8/7)^n

b) (-3/4)^n=81/256

 

Answer 1

a)-512=-8^3

   343=7^3

=>-512/343=(-8/7)^3

=>n=3

   Vậy n=3

b)ta có : 81=(-3)^4

              256=4^4

=>81/256=(-3/4)^4

=>n=4

          Vậy n=4

Answer 2

a) \(-\frac{512}{343}=\left(-\frac{8}{7}\right)^n\)

\(\Rightarrow\left(\frac{8}{7}\right)^n=\frac{512}{343}\)

\(\Rightarrow\left(-\frac{8}{7}\right)^n=\left(\frac{8}{7}\right)^3\)

=> n = 3

b) \(\left(-\frac{3}{4}\right)^n=\frac{81}{256}\)

\(\Rightarrow\left(-\frac{3}{4}\right)^n=\left(\frac{3}{4}\right)^4\)

=> n = 4