Mathematics in Business and Economics
Indices or Powers
Indices or powers show how many times a number is multiplied by itself. 13³ means 13 x 13 x 13.
- To multiply numbers with different powers (for example, 4² x 4³) simply add the powers together - the answer in this case is 45.
- Any number to the power of 0 = 1.
- Negative powers require us to understand the relationship between multiplying and dividing. A negative power, for example, 2-3 is the same as ½³.
- When dividing same numbers with powers, subtract the powers, e.g. 25 ÷ 2² = 2³.
- If multiplying same numbers with a mix of positive and negative powers, add together the powers.
- With powers of negative numbers, (-5)² = -5 x -5. A minus times a minus gives a plus and 5 x 5 = 25. The answer therefore is 25.
- Negative numbers raised to odd powers (such as (-2)3) will have a negative sign. Again this is because of the rule of multiplying positive and negative numbers. (-2)3 = -2 x -2 x -2 which is a negative number times a negative number (-2 x -2 = 4) and then this multiplied by another negative number (4 x -2). So the answer is -8.
Summary of the Rules
(Py)z = Pyz
(PT)y = Py Ty
z√Py = Py/z or (P1/z)y
√P = P½
Py x Pz = Py+z
y√P = P1/y