There are a number of words that algebra uses:
term is a variable, normally a letter, which is used as a placeholder for an unknown number. It may have a multiplier (called a coefficient) and be set to a power: x, 3x and 5x2 are all terms;
expression is a collection of more than one term: 3x + 5y is an expression, as is 2x2 + 5x. An expression does not have an equals sign;
an equation has an equals sign, and the value(s) of the variables, or letters, can be worked out by solving the equation. 5x - 3 = 2 is an equation: the value of x can be solved;
formula determines one value given other values. Although it has an equals sign, it differs from an equation because the other values determine the value of the unknown variable. A = `frac(1)(2)`bh is a formula.
An inequality gives a set of answers for an algebraic statement. For example, x > 12 is an inequality: and 13, 14, 15, 16 are all valid answers for that statement.
Advanced students: an identity is an expression that is written in another form.
x2 + x - 6 = (x + 3)(x - 2) is an identity:
whichever value of x is chosen, the equation remains true. It is not possible to find a solution to an equation if it is an identity.
1. Is 3x2 + 4xy a term, an expression or a formula?
Answer: An expression
There is more than one term.
2. Is d = vt + `frac(1)(2)`at2 an equation or a formula?
Answer: It is a formula
You can work out the value of d given the other values.