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.

The rules

• 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

	P		y	=	Py
	T				Ty

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