Addition and subtraction are mathematical processes. They can be used in equations, which are statements that the values of two mathematical expressions are equal, but they are not equations by themselves.
expressions don't have an equal sign and equations do
Equations are made from expressions.
In the same way that you would solve equations because equivalent expressions are in effect equations
no algebraic expressions do not have equal signs but equations do.
These are two expressions, not equations. Expressions do not have solutions, only equations do. NB equations include the equals sign.
It may be possible to solve equations. Expressions cannot be solved until they are converted, with additional information, into equations or inequalities which may have solutions.
a rational function.
Both have a value
They both have numbers and symbols
They can, but don't have to.
No they do not, equations have equal signs.