Usually terms with the highest power (exponent), are written on the left, for example, formula_8 is written to the left of . When a coefficient is one, it is usually omitted (e.g. formula_9 is written formula_8). Likewise when the exponent (power) is one, (e.g. formula_11 is written formula_12). When the exponent is zero, the result is always 1 (e.g. formula_13 is always rewritten to ). However formula_14, being undefined, should not appear in an expression, and care should be taken in simplifying expressions in which variables may appear in exponents.