## Precalculus (6th Edition) Blitzer

Domain:$\quad (-\infty, 7) \cup (7, \infty)$ or, $\{x\in \mathbb{R}\ |\ x\neq 7\}$
Logarithmic functions are defined for positive arguments only. The argument here is $(x-7)^{2}$, which is never negative. The only problem is when it is zero. So, the domain is all reals except $7$. Domain:$\quad (-\infty, 7) \cup (7, \infty)$ or, $\{x\in \mathbb{R}\ |\ x\neq 7\}$