Presented by Dr. Del Ferster

 We’ll spend a bit of time looking at some “test-type” problems.  We’ll refresh some basic properties of exponents ◦ Fractional powers and radicals ◦ Negative powers  We’ll spend a bit of time on rates of change ◦ For linear functions, this is SLOPE  Then, we’ll look at some problems that deal with rates of change.

Practice Problems Properties of Exponents and Rate of Change

 1., so C  2., so A  3., so B

 4.need 3 gallons, so B  minutes, so A  6.15 points per hour, so C  7.B

 8., so A  9.16 feet per second, so D  feet per second, so C

 Free Response Questions  1.  2A.$10,800 profit per summer  2B.3 summers

Properties of Exponents Negative powers, and fractional powers

 How do we handle negative exponents?  Is there a way to write radical expressions as exponential forms, and vice versa?

If a ≠ 0 is any real number and n is a positive integer, then In effect, any base that has a negative power, gets relocated. If it was originally on top of the fraction, it moves to the bottom. After the move, the power goes positive.

Simplify each expression. Your final answer should have no negative powers.

For example, and, For example,

First, rewrite as a radical, then simplify each expression.

Rates Of Change

 What do we mean when we give a rate of change?  What kinds of things have a CONSTANT rate of change?  What are some examples of rate of change, that we use in “everyday life”?

When you have two variables changing values at the same time, the rate of change describes the rate at which the first variable is changing compared to the rate at which the 2 nd variable is changing.

 Change in the dependent variable Change in the independent variable  Vertical change Horizontal change 

A line has a positive rate of change if the line is increasing from left to right. A line has a negative rate of change if the line is decreasing from left to right. Types of rate of change A line has a zero (0, or no) rate of change if the line is horizontal. A line has an undefined rate of change if the line is vertical.

 The words GRADIENT and RATE and SLOPE all mean exactly the same thing.  If you can solve for one of these, you can solve for any, because they’re all the same.

 Here are the basics: 1.There will always be 2 variables (numbers) 2.Gradient means “How does a change in one variable affect the other?” 3.To get the answer you will usually have to subtract (to get the change) and 4.you will almost always have to divide (to fine the affect).

 IF you can subtract and divide then you can solve all gradient/rate/slope (or more impressively, rate of change) problems! We begin with word problems. The trick here is to read carefully and to figure out what to do with the information you are given. Remember: You may have to SUBTRACT. You will almost always have to DIVIDE.

 An balloon rises 1000 meters in 5 minutes. At what rate is it rising?  Express your answer in meters per minute.

 Five seconds into flight, a rocket is 2,000 feet above the earth. Twenty five seconds into flight, the rocket is 42,000 feet above the earth. How fast is the rocket rising (in feet per second)?

 A balloon is released at an altitude of 500 meters at 2:15. At 2:45 the balloon had an altitude of 3500 meters. Find the rate at which the balloon is rising.

 Now, let’s explore the concept, when the data is provided by a graph. A student released a balloon and recorded data on the graph at the left. According to the graph at what rate did the balloon rise from time 2 minutes to time 7 minutes?

 Remember: ◦ There are always 2 variables (numbers). ◦ One is called the DEPENDENT VARIABLE ◦ This is usually y  When dividing, this one goes on TOP. ◦ The other is called the INDEPENDENT VARIABLE. ◦ This is usually x or t  It goes on the bottom.

Do rates of change remain constant?

Consider the graph to the left. Let’s explore this question: Does the rate change over time? To find out let’s calculate the rate of change for several different time periods and see if it changes.

 First what is the rate from time 0 to time 4?  How about the rate from time 3 to time 6?  Ok, one more, how about from time 2 to time 9?

 Did the rate change over time?

 How can the rate be the same when that line is OBVIOUSLY going UP? ◦ Remember, that RATE is SLOPE! ◦ If you were a skier going down that black line, would you think that the slope was changing?  In other words, is the line “STEEPER” in some places than others?

The slope of the line stays the same, and since slope and rate are really the same thing, the rate must stay the same as well. If the slope doesn’t change, then the rate doesn’t change. Can you draw a graph, that would indicate a change in the rate? What could it look like?

Graph AGraph B Consider these two graphs. 1.Is the rate in each graph changing? 2.Something is different though, what?

 It appears that the slope of the line in graph B is steeper than the slope of the line in graph A.  The STEEPER the slope, the GREATER (FASTER) the rate of change.

The “line” on this graph isn’t straight, what does this mean? Is the slope increasing or decreasing? Imagine that you were riding the bike up this slope, would you say that it is getting steeper or less steep?

The scales are the same, the labels are the same, so what’s the difference?

 The graph on the left represents the RATE of a car going 50 miles in 1 hour (50 mi/hr)  The graph on the right represents the RATE of a car going 20 miles in 1 hour (20 mi/hr).  Since the slope of the graph on the right is less steep than the slope of the graph on the left, the car’s RATE is less ◦ In summary: Constant slope = constant rate; Steep = Fast; less steep = slower.

The scales are the same, the labels are the same, so what’s the difference?

 The graph on the left represents a car moving at a constant speed. ◦ We know this because slope is rate and slope is c_____  In the graph on the right the slope does change. ◦ It starts off fairly flat, then the slope gets steeper and steeper. ◦ What does this mean?

 1. Find the rate of change for the data in the table below. TicketsCost 5$75 6$90 7$105 8$120

2. Find the rate of change for the data in the graph.

3. Find the slope of the line.

 1.  2.  3. $15 per ticket 400 calories per hour 4343

 I’ve compiled a packet of problems that allow us refine our skills related to rates of change.  Some problems are good for middle school grades, some for high school grades. ◦ With some editing on your part, the middle school ones can be used with higher elementary grades, I think.  Frankly, I think this is what we should spend time on with our students.

 Thanks for your attention and participation. ◦ You have my utmost respect for working hard all day with your kids, and still hanging in there for what we’ve done!  If I can help in any way, don’t hesitate to shoot me an , or give me a call.