1. Number Theory and the Real Number System
CHAPTER 5
Number Theory and the Real Number System

2. Exponents and Scientific Notation
5.6
Exponents and Scientific Notation

3. Objectives
Use properties of exponents.
Convert from scientific notation to decimal notation.
Convert from decimal notation to scientific notation.
Perform computations using scientific notation.
Solve applied problems using scientific notation.

4. Properties of Exponents
Property
Meaning
Examples
The Product Rule
bm · bn = bm + n
When multiplying exponential expressions with the same base, add the exponents. Use this sum as the exponent of the common base.
96 · 912 =
= 918
The Power Rule
(bm)n = bmn
When an exponential expression is raised to a power, multiply the exponents. Place the product of the exponents on the base and remove the parentheses.
(34)5 = 34·5 = 320
(53)8 = 53·8 = 524
The Quotient Rule
When dividing exponential expressions with the same base, subtract the exponent in the denominator from the exponent in the numerator. Use this difference as the exponent of the common base.

5. The Zero Exponent Rule
If b is any real number other than 0, b0 = 1.

6. Example: Using the Zero Exponent Rule
Use the zero exponent rule to simplify: a. 70=1 b. c. (5)0 = 1 d. 50 = 1

7. The Negative Exponent Rule
If b is any real number other than 0 and m is a natural number,

8. Example: Using the Negative Exponent Rule
Use the negative exponent rule to simplify: c.

9. Powers of Ten
A positive exponent tells how many zeros follow the 1. For example, 109, is a 1 followed by 9 zeros: 1,000,000,000.
A negative exponent tells how many places there are to the right of the decimal point. For example, 10-9 has nine places to the right of the decimal point.
10-9 =

10. Scientific Notation
A positive number is written in scientific notation when it is expressed in the form a  10n , where a is a number greater than or equal to 1 and less than 10 (1 ≤ a < 10), and n is an integer.

11. Convert Scientific Notation to Decimal Notation
If n is positive, move the decimal point in a to the right n places. If n is negative, move the decimal point in a to the left |n| places.

12. Example: Converting from Scientific to Decimal Notation
Write each number in decimal notation: a  1010 b. 1.1  10-4 In each case, we use the exponent on the 10 to move the decimal point. In part (a), the exponent is positive, so we move the decimal point to the right. In part (b), the exponent is negative, so we move the decimal point to the left.

13. Converting From Decimal to Scientific Notation
To write the number in the form a  10n: Determine a, the numerical factor. Move the decimal point in the given number to obtain a number greater than or equal to 1 and less than 10. Determine n, the exponent on 10n. The absolute value of n is the number of places the decimal point was moved. The exponent n is positive if the given number is greater than or equal to 10 and negative if the given number is between 0 and 1.

14. Example: Converting from Decimal Notation to Scientific Notation
Write each number in scientific notation: a. 4,600,000 b Solution:

15. Computations with Scientific Notation
We use the product rule for exponents to multiply numbers in scientific notation: (a 10n)  (b  10m) = (a  b)  10n+m Add the exponents on 10 and multiply the other parts of the numbers separately.

16. Example: Multiplying Numbers in Scientific Notation
Multiply: (3.4  109)(2  10-5). Write the product in decimal notation. Solution: (3.4  109)(2  10-5) = (3.4  2)(109  10-5) = 6.8  109+(-5) = 6.8  104 = 68,000

17. Computations with Scientific Notation
We use the quotient rule for exponents to divide numbers in scientific notation: Subtract the exponents on 10 and divide the other parts of the numbers separately.

18. Example: Dividing Numbers In Scientific Notation
Divide: . Write the quotient in decimal notation. Solution:
Regroup factors.
Subtract the exponents.
Write the quotient in decimal notation.

19. Example: The National Debt
As of December 2011, the national debt was $15.2 trillion, or 15.2  1012 dollars. At that time, the U.S. population was approximately 312,000,000, or 3.12  108. If the national debt was evenly divided among every individual in the United States, how much would each citizen have to pay? Solution: The amount each citizen would have to pay is the total debt, 15.2  1012, divided among the number of citizens, 3.12  108.

20. Example: The National Debt continued
Every citizen would have to pay approximately $48,700 to the federal government to pay off the national debt.