POWERS. 3º ESO

Exponents

The exponent of a number says how many times to use the number in a multiplication.

In 8² the "2" says to use 8 twice in a multiplication,
so 8² = 8 × 8 = 64

In words: 8² could be called "8 to the power 2" or "8 to the second power", or simply "8 squared"

Exponents are also called Powers or Indices.

Some more examples:

Example: 5³ = 5 × 5 × 5 = 125

• In words: 5³ could be called "5 to the third power", "5 to the power 3" or simply "5 cubed"

Example: 2⁴ = 2 × 2 × 2 × 2 = 16

• In words: 2⁴ could be called "2 to the fourth power" or "2 to the power 4" or simply "2 to the 4th"

Exponents make it easier to write and use many multiplications.

Negative Exponents

In General

That last example showed an easier way to handle negative exponents: Calculate the positive exponent (an) Then take the Reciprocal (i.e. 1/an)

More Examples:

Negative Exponent		Reciprocal of Positive Exponent		Answer
4-2	=	1 / 42	=	1/16 = 0,0625
10-3	=	1 / 103	=	1/1.000 = 0,001
(-2)-3	=	1 / (-2)3	=	1/(-8) = -0,125

Be Careful About Grouping

To avoid confusion, use parentheses () in cases like this:

With () :	(-2)2 = (-2) × (-2) = 4
Without () :	-22 = -(22) = - 2 × 2 = -4

With () :	(ab)2 = ab × ab
Without () :	ab2 = a × (b)2 = a × b × b

What if the Exponent is 1, or 0?

1		If the exponent is 1, then you just have the number itself (example 91 = 9)
0		If the exponent is 0, then you get 1 (example 90 = 1)
		But what about 00 ? It could be either 1 or 0, and so people say it is "indeterminate". SOME EXERCISES:    http://www.mathopolis.com/questions/quiz.php Laws of Exponents Here are the Laws (explanations follow): Law Example x1 = x 61 = 6 x0 = 1 70 = 1 x-1 = 1/x 4-1 = 1/4 xmxn = xm+n x2x3 = x2+3 = x5 xm/xn = xm-n x6/x2 = x6-2 = x4 (xm)n = xmn (x2)3 = x2×3 = x6 (xy)n = xnyn (xy)3 = x3y3 (x/y)n = xn/yn (x/y)2 = x2 / y2 x-n = 1/xn x-3 = 1/x3 And the law about Fractional Exponents: AND SOME MORE EXERCICES: http://www.mathopolis.com/questions/q.php?id=2866  http://www.mathopolis.com/questions/quiz.php