Question

Tìm x

Answer 1

1) \(2^x=4^3\)

\(2^x=\left(2^2\right)^3\)

\(2^x=2^6\)

`=>x=6`

4) \(2^x=8^3\)

\(2^x=\left(2^3\right)^3\)

\(2^x=2^9\)

`=>x=9`

7) \(\left(\dfrac{1}{7}\right)^x=\left(\dfrac{1}{343}\right)^3\)

\(\left(\dfrac{1}{7}\right)^x=\left[\left(\dfrac{1}{7}\right)^3\right]^3\)

\(\left(\dfrac{1}{7}\right)^x=\left(\dfrac{1}{7}\right)^9\)

`=>x=9`

10) \(\left(\dfrac{6}{7}\right)^x=\left(\dfrac{216}{343}\right)^{111}\)

\(\left(\dfrac{6}{7}\right)^x=\left[\left(\dfrac{6}{7}\right)^3\right]^{111}\)

\(\left(\dfrac{6}{7}\right)^x=\left(\dfrac{6}{7}\right)^{333}\)

`=>x=333`

13) \(2^{5x+2}=8^9\)

\(2^{5x+2}=\left(2^3\right)^9\)

\(2^{5x+2}=2^{27}\)

`=>5x+2=27`

\(5x=27-2=25\)

`=>x=25/5=5`

16) \(2^{7x+4}=32^{12}\)

\(2^{7x+4}=\left(2^5\right)^{12}\)

\(2^{7x+4}=2^{60}\)

`=>x=7x+4=60`

\(7x=60-4=56\)

`=>x=56/7=8`

19) \(4^{-1-5x}=16^{12}\)

\(4^{-1-5x}=\left(4^2\right)^{12}\)

\(4^{-1-5x}=4^{24}\)

`=>-1-5x=24`

\(5x=\left(-1\right)-24=-25\)

`=>x=(-25)/5=-5`