Question

Tìm x:

a) \(\left(5x-1\right)^6=729\) b) \(\dfrac{8}{25}=\dfrac{2^x}{5^{x-1}}\) c) \(\left(\dfrac{1}{16}\right)^x=\left(\dfrac{1}{2}\right)^{10}\) d) \(9^x:3^x=3\)

Answer 1

a,\(\left(5x-1\right)^6=729\)

\(\left(5x-1\right)^6=3^6\)

\(5x-1=3\)

\(5x=4\)

\(x=\dfrac{4}{5}\)

Answer 2

b Ta có \(8=2^3\),\(25=5^2\)

Mà \(\dfrac{8}{25}=\dfrac{2^x}{5^{x-1}}\)

=> \(2^3=2^x,5^2=5^{x-1}\)

=> x=3

Answer 3

c Ta có \(16=2^4\)

hay \(\left(\dfrac{1}{2^4}\right)^x=\left(\dfrac{1}{2}\right)^{10}=>x\cdot4=10=>x=\dfrac{10}{4}=\dfrac{5}{2}\)

Answer 4

d \(9^x:3^x=3=>3^{2\cdot x}:3^x=3=>2\cdot x-x=1=>x=1\)