Basic Exponents




Exponential Notation

Exponential notation simplifies repeated multiplication. Below is an example of an exponent:

2^{3}=2\cdot2\cdot2=8

In the above expression, 2 is the base and 3 is the exponent. You would read 2^{3} as: “two raised to the power of three,” or “two to the third.” As shown above, 2^{3}, equals two times two times two.

Using generic terms x^{n} is equal to 1 multiplied by x \; n times.

This list of powers of two should help you see the pattern.

2^{0}=1\\2^{1}=1\cdot2=2\\2^{2}=1\cdot2\cdot2=4\\2^{3}=1\cdot2\cdot2\cdot2=8\\2^{4}=1\cdot2\cdot2\cdot2\cdot2=16\\2^{5}=1\cdot2\cdot2\cdot2\cdot2\cdot2=32

Can you figure out what 2^{6} is?

Because the placeholding 1 does not affect the outcome, it is usually not written; we’re using it here only to help demonstrate the pattern.

You may be stumped as to why 2^{0}=1. In fact, any number raised to the power of 0 equals 1. If you refer to our definition of the notation, x^{0} is equal to 1 times x zero times, so there is no multiplication and we are only left with 1.

If x is negative, the notation works the same but we must use parentheses correctly. For example:

(-3)^{2}=1\cdot-3\cdot-3=9

but,

-3^{2}=-1\cdot3^{2}=-1\cdot3\cdot3=-9

It is important to to notice how the parentheses affect the outcome. In the first example -3 is squared. In the second example only 3 is squared, and the negative sign is applied to that result.

Now what if n is negative? For example 2^{-3}. In this case you would simply divide 1 by two three times.

2^{-3}=1/2/2/2=\frac{1}{2\cdot2\cdot2}=\frac{1}{8}

Using the generic number x and n we have the definition:

Since division is the opposite of multiplication, if your exponent is negative, you divide 1 by x n times. This list of some of the positive and negative powers of three will help show the pattern.

3^{-3}=\frac{1}{3\cdot3\cdot3}=\frac{1}{27}\\3^{-2}=\frac{1}{3\cdot3}=\frac{1}{9}\\3^{-1}=\frac{1}{3}\\3^{0}=1\\3^{1}=1\cdot3=3\\3^{2}=1\cdot3\cdot3=9\\3^{3}=1\cdot3\cdot3\cdot3=27

Square Roots

Any number raised to the power of 2 is said to be ‘squared.’ Taking a square root of a number reverses the process or ‘squaring.’ For Example:

4^{2}=16 \quad \sqrt{16}=4

Here’s an example of solving a basic equation for x:

x^{2}=81\\\rightarrow \sqrt{x^{2}}=\sqrt{81}\\\rightarrow x=9\\(\text{because,\;} 9^{2}=81)

Scientific Notation

It is not practical to write out really long numbers, like 42,000,000,000,000,000,000,000,000,000,000. Instead we use scientific notation to eliminate all the zeros. In scientific notation, this number becomes 4.2\cdot10^{31}, which conserves a lot of space.

Notation aside, both numbers are mathematically equal, one merely uses exponential notation to eliminate the tail zeros. If you count the digits to the right of 4 you’ll come up with 31: this is no coincidence. 10^{31}=10,000,000,000,000,000,000,000,000,000,000 so when you multiply 4.2 by 10^{31} you get 42,000,000,000,000,000,000,000,000,000,000. Take a look at these examples and try to spot the general pattern.

175,020,000,000=1.7502\cdot10^{11}

23,000=2.3\cdot10^{4}

1,000,000,000=1\cdot10^{9}

5,056,700,000,000,000=5.0567\cdot10^{15}

You can also use scientific notation on very small numbers. The method is the similar but you’re working backwards and so negative powers of ten are used. Here are some examples:

0.00001=1\cdot10^{-5}

0.0000007708=7.708\cdot10^{-7}

0.000001005=1.005\cdot10^{-6}

The principle of scientific notation is that multiplication or division by 10 moves the decimal place in a number. Refer to the study guide on decimals for a more detailed discussion on this.

You have likely seen numbers in scientific notation before on your calculator. Since calculator screens are not large enough to display very large numbers, calculators use scientific notation to display oversize numbers. For example, the BA II Plus can only fit 10 digits on the screen; anything larger must be displayed using scientific notation. If you calculate 1,000,000^{2} on this model the screen displays: 1.\;12, this means: 1\cdot10^{12}, or: 1,000,000,000,000. Other models will give similar messages once their screen capacities’ are surpassed; some may use a format like: 1\;\text{E}12.

Practice Questions

Learn to use your calculator to compute exponents and square roots. Look for keys with symbols like these: \wedge,\;y^{x},\;\sqrt{x}.

Simplify the following:

1.) 4^{3}

2.) 4^{-3}

3.) 3^{5}

4.) 7^{-3}

5.) 10^{6}

6.) 10^{-2}

7.) (-2)^{3}

8.) -3^{3}

9.) (-3)^{-4}

10.) \sqrt{64}

11.) \sqrt{16}

12.) \sqrt{5^{2}}

Convert the following numbers into scientific notation:

13.) 1,002,000,000

14.) 12,034,500,000,000

15.) 0.0000088

16.) 0.0011

Convert the following numbers into standard notation:

17.) 5.6092\cdot10^{8}

18.) 1.0011\cdot10^{4}

19.) 3.79\cdot10^{-6}

20.) 6.1602\cdot10^{-10}

Solutions