Solve 4^x=128

$$4 ^ { x } = 128$$

Solve for x

$$x = \frac{7}{2} = 3\frac{1}{2} = 3.5$$

Steps Using Definition of Logarithm

Use the rules of exponents and logarithms to solve the equation.

$$4^{x}=128$$

Take the logarithm of both sides of the equation.

$$\log(4^{x})=\log(128)$$

The logarithm of a number raised to a power is the power times the logarithm of the number.

$$x\log(4)=\log(128)$$

Divide both sides by \log(4).

$$x=\frac{\log(128)}{\log(4)}$$

By the change-of-base formula \frac{\log(a)}{\log(b)}=\log_{b}\left(a\right).

$$x=\log_{4}\left(128\right)$$

Solve for x (complex solution)

$$x=\frac{\pi n_{1}i}{\ln(2)}+\frac{7}{2}$$

$$n_{1}\in \mathrm{Z}$$