Chapter 1 - Section 1.2 - Operations with Real Numbers and Simplifying Algebraic Expressions - Exercise Set - Page 29: 161

Equivalent algebraic expressions are expressions that will give the same value for any real number replacement for the variable/s.

Equivalent algebraic expressions are expressions that will give the same value for any real number replacement for the variable/s. Example: $2x+1$ and $1+2x$ are equivalent algebraic expressions since for any real number $x$, their values would be the same.