GCSE(F),

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*, 3*x* and 5*x*^{2} are all terms;

**expression** is a collection of more than one term: 3*x* + 5*y* is an expression, as is 2*x*^{2} + 5*x*. 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. 5*x* - 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.

*x*^{2} + *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 3*x*^{2} + 4*xy* a term, an expression or a formula?

Answer: An expression

There is more than one term.

2. Is *d* = *vt* + `frac(1)(2)`*at*^{2} an equation or a formula?

Answer: It is a formula

You can work out the value of *d* given the other values.

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