Logarithm Change Base
1. **Stating the problem**: Given $\log_4 x = y$, where $x > 0$, find:
a) $\log_2 x$
b) $\log_8 x$
c) $\log_{16} x$
2. **Express $x$ in terms of $y$:**
$$\log_4 x = y \implies x = 4^y$$
3. **Rewrite $4$ in base $2$:**
$$4 = 2^2$$
So,
$$x = (2^2)^y = 2^{2y}$$
4. **Compute each requested logarithm:**
a) $\log_2 x = \log_2 (2^{2y}) = 2y$
b) Rewrite $8$ as $2^3$, then use change of base:
$$\log_8 x = \log_8 (2^{2y}) = \frac{\log_2 (2^{2y})}{\log_2 8} = \frac{2y}{3}$$
c) Rewrite $16$ as $2^4$, then similarly:
$$\log_{16} x = \log_{16} (2^{2y}) = \frac{\log_2 (2^{2y})}{\log_2 16} = \frac{2y}{4} = \frac{y}{2}$$
**Final answers:**
a) $\log_2 x = 2y$
b) $\log_8 x = \frac{2y}{3}$
c) $\log_{16} x = \frac{y}{2}$