Chapter 2 - Functions - 2.2 Domain and Range - Exercises and Problems for Section 2.2 - Exercises and Problems - Page 82: 10

All real numbers except positive and negative 2.

To find domain restrictions, we look for any numbers that make the denominator of a fraction 0 or the expression under the square root sign negative. Thus, we find: $$ t^2=4 \\ t=\pm2$$