SOLUTION: what are differences between expressions and functions? if we can find solution to expression in order to find the variable why functions were introduced?

Question 893224: what are differences between expressions and functions? if we can find solution to expression in order to find the variable why functions were introduced?
Answer by josgarithmetic(39616) (Show Source): You can put this solution on YOUR website!
An expression is like a phrase or a clause; a function is like a sentence.
One can evaluate an expression; and one can evaluate a function for a given value for an input variable.

Another attempt:

An expression is a number. The number can be written with plain numbers and variables, or it can be written just in variables.
, , , or any such way of writing a number is an expression.

A function is, for your purpose, a statement usually using symbols and numbers, that some number with a name is equal to an expression. The name for the function is given a letter like f, or g, or h, or sometimes other letters.
f(x) or g(x) or h(x) is a name of a function. A function is often written as an equation, for example:
or or .
The left side of the equation is a number. The right side of the equation is a number.

We can use functions to say that a quantity (the name of the function) depends on the value of a variable.
If we have a function like , then this means the value of f depends on the value of x.
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If we want x=-3, then we can find , which means .
If we want x=7, then we can find , which is .
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