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1. A Review of Our Number Systems and an Introduction to e

2. This PowerPoint contains notes, examples and practice problems for you to complete. It is important that you slowly work through this PowerPoint and not just move through it quickly. This is your chance to practice this material, so you must work through it and learn it! Remember that, as you work through this PowerPoint, do not go onto the next part until you are certain that you understand what is being presented. Also, do not look at any answers until you have tried the problem yourself. If you have any questions, ask your teacher!

3. Part I: Reviewing Our Different Number Systems

4. Can you write down two examples of the following types of numbers: Real Numbers: Rational Numbers: Integers: Irrational Numbers: Imaginary Numbers: Complex Numbers: When you believe you have two examples for each type, please check your answers.

5. Now, discuss and answer the following questions in your notebook: 1. How do we define a complex number or what is the definition of a complex number? 2. How do we define a rational number or what is the definition of a rational number? 3. How do we define an irrational number or what is the definition of a irrational number? When you are ready, look at the next slide for possible answers. If you are unsure, ask!

6. Now, discuss and answer the following questions in your notebook: 1. How do we define a complex number or what is the definition of a complex number? A complex number is written in the form where a is a real number and bi is an imaginary number. 2. How do we define a rational number or what is the definition of a rational number? A rational number is a real number which is written as a fraction or in the form where a and b are both integers. 3. How do we define an irrational number or what is the definition of an irrational number? An irrational number is a real number which cannot be written as a rational number or it cannot be written in the form where a and b are both integers.

7. Now, write in the following types of numbers into the diagram below: 1. Real Numbers 2. Integers 3. Rational Numbers 4. Irrational Numbers 5. Imaginary Numbers 6. Complex Numbers The entire grey rectangle and everything in it. Both the grey and blue rectangles combined Just the grey part of the rectangle. Just the blue rectangle Both the white and blue parts. Just the blue part. When you are finished, the next slide has the answer.

8. Now, write in the following types of numbers into the diagram below: 1. Real Numbers 2. Integers 3. Rational Numbers 4. Irrational Numbers 5. Imaginary Numbers 6. Complex Numbers The entire grey rectangle and everything in it. Both the grey and blue rectangles combined Real Numbers Complex Numbers Just the grey part of the rectangle. Just the blue rectangle Irrational Numbers Imaginary Numbers Rational Numbers Both the white and blue parts. Just the blue part. Integers

9. Part II: An Introduction to e

10. Using your calculator, complete the following table in your notebook for the following exponential function: Try the first row then look at my answer to see if you are correct. Give your answers to 5 decimal places! If you are correct, keep working and check your answers when you are finished. If you are incorrect, ask your teacher. 2.59374 2.70481 2.71692 2.71814 2.71827 2.71828 2.71828

11. Did you notice anything about your answer as you made x larger and larger? Discuss this with your partner. So, If we evaluate this function with larger and larger values of n, this function eventually approaches a number. This number that the function approaches is an irrational number. Since it is an irrational number, it cannot be written as a fraction and is found in a lot of different mathematical equations. Because it is used so often, it is given a special letter, the letter e. This is an important number to know and is used frequently in higher level mathematics classes. Here is an approximate value of e =

12. The number e is also in your calculator. It is found in two places. They are: Here Here

13. Let’s find the following values using our calculator. Remember to use parentheses if they are needed! For example, the value: will be evaluated in our calculator as shown below: Notice the parentheses that are used when typing the value into your calculator. Without the parentheses, your answer will be wrong! So:

14. Find the following values using our calculator. Remember to use parentheses if they are needed! Find: Answers: Find: Answers:

15. Part III: An Example of How We Will Use the Number e

16. Remember the basic formula for exponential Growth and Decay Let’s invest \$1000 at a rate of 5% for 10 years. Use this information to complete the following table: \$1628.89 \$1643.62 \$1647.01 \$1648.66 \$1648.72 \$1648.72

17. The values in this table are all values for discrete exponential growth. These are problems where the growth or decay is evaluated at a particular time. As we increased the number of times we evaluated the exponent, the values began to approach a number. This number is related to the number e. When we evaluate exponential growth continuously, or, instead of every minute, or every second, but all of the time, we use a formula with e. Continuous exponential growth can be found using the formula: So, if a problem specifically states that it is found using continuous growth or decay, then use this formula. If it does not state continuous growth or decay, then use the discrete formulas we have used earlier.

18. Here is an example, that we can solve together. The number of bacteria cells in a culture grows continuously at a rate of 2.31% per day. If 25 cells are present now, approximately how many are present after 12 days? Notice that this problem states that it is growing continuously. If it did not state that the growth is continuous, then we would use our basic exponential growth or decay formula. So, find the following values: So, we have the formula: using our calculator Answer: 33.0 cells

19. Here is an example, that we can solve together. The population of a country grows continuously at a rate of 2.12% per year. If the country currently has 5.7 million people, how many people will there be after 5 years? Notice that this problem states that it is growing continuously. If it did not state that the growth is continuous, then we would use our basic exponential growth or decay formula. So, find the following values: So, we have the formula: using our calculator Answer: 6.34 million people

20. Here is an example, that we can solve together. If I invest \$1000 in an account that pays 5% annual interest, how much do I have in the account after 3 years? Notice that this problem does NOT state that it is growing continuously. So, we will use our basic exponential growth or decay formula with the following values: So, we have the formula: using our calculator Answer: \$1157.63

21. The number of trees in a forest grows continuously at a rate 1.2% per year. If there are 2,350 trees in the forest now, how many trees were there in the forest 12 years ago? Answer: 2030 trees The price of a computer increases at a rate of 7.3% annually. If the price of the computer is \$1600 now how much will it cost in 3 years and 4 months? Answer: \$2023.57 Notice that this question does NOT use the word continuous in it. It is NOT continuous growth but discrete growth and so we use the basic formula for discrete growth, or: where n = 1, or once a year.

22. The number of bacteria in a culture is decaying continuously at a rate of 2.67% per day. If the culture currently has 350 cells, how many cells were there in the culture 13 days ago. Answer: 495 cells A radioactive isotope is decaying continuously at a rate of .0051% per year. If 2 kg is present now, how much is present after 150 years? Answer: 1.98 kg

23. The number of people who attend a university grows continuously at a rate of 1.2% each year. If 5600 people currently attend the university now, how many students attended 5 years ago? Answer: 5270 people The price of a car decreases at a rate of 11% annually. If the price of the car is \$4500 now how much will it cost in 4 years? Answer: \$2823.40 Notice that this question does NOT use the word continuous in it. It is NOT continuous growth but discrete growth and so we use the basic formula for discrete growth.