How are algebraic expressions and equations alike?
Algebraic expressions are the written relations of or between
variables. For example, x2, 1/x, and x + y + z are all algebraic
expressions. Algebraic equations are simply algebraic expressions
that equate to something. For example, x2 = 4, 1/x = y, and x + y +
z = 42 are all algebraic equations. In general, one differentiates
algebraic expressions from exponential, trigonometric, hyperbolic,
and logarithmic expressions by requiring algebraic expressions to
be confined to polynomial expressions. I've added a link regarding
polynomials below.