Algebra II: 2-4 Writing Linear Equations Date: Forms of Equations Consider the following graph. The line passes through and. Notice that is the y-intercept of. You can use these two points to find the slope of. Find the slope: Now solve your new equation for y. This form is called the. Example #1: Write an Equation Given Slope and a Point Write an equation in slope-intercept form for the line that has a slope of through (5, - 2). 3 5 and passes 1
Point-slope form: use this form to find an equation of a line when you are given the of two on a line Example #2: Write an Equation Given Two Points Write an equation of the line through (2, - 3) and ( - 3, 7). When changes in real-world situations occur at a equation can be used as a for describing the situation., a linear Example #3: Write an Equation for a Real-World Situation Sales As a part-time salesperson, Jean Stock is paid a daily salary plus commission. When her sales are $100, she makes $58. When her sales are $300, she makes $78. a) Write a linear equation to model this situation. b) What are Ms. Stock s daily salary and commission rate? c) How much would Jean make in a day if her sales were $500? 2
Parallel and Perpendicular Lines The and forms can be used to find equations of lines that are or to given lines. Example #4: Write an Equation of a Perpendicular Line Write an equation for the line that passes through (3, - 2) and is perpendicular to the lien whose equation is y = 5 x + 1. 3
Date: Algebra II 2-5: Modeling Real-World Data: Using Scatter Plots Real Numbers Data with two variables, is called. A set of bivariate data graphed as ordered pairs in a coordinate plane is called a. A scatter plot can show whether there is a between the data. Example #1: Draw a Scatter Plot Education The table shows the approximate percent of students who sent applications to two colleges in various years since 1985. Make a scatter plot of the data. Prediction Equations When you find a line that closely approximates a set of, you are finding a for the data. An equation of such a line is often called a because it can be used to predict one of the variables given the other variable. To find a line of fit and a prediction equation for a set of data, select that appear to represent the data well. This is a matter of personal judgment, so your line and prediction equation may be different from someone else s. Example #2: Find and Use a Prediction Equation 4
Education Refer to the data in Example #1. a) Draw a line of fit for the data. How well does the line fit the data? b) Find a prediction equation. What do the slope and y-intercept indicate? c) Predict the percent in 2010. d) How accurate is the prediction? 5
Date: Algebra II 2-6: Special Functions Step Functions, Constant Functions, and the Identity Function The cost of postage to mail a letter is a of the weight of the letter. But the function is not. It is a special function called a. The graph of a step function is not. It consists of line segments or rays. The, written, is an example of a step function. The symbol means the greatest integer less than or equal to x. For example, and because. Study the table and graph below. Example #1: Step Function Psychology One psychologist charges for counseling sessions at the rate of $85 per hour or any fraction thereof. Draw a graph that represents this situation. 6
You ve learned that the slope-intercept form of a linear function is, or in functional notation,. When m=0, the value of the function is for every x value. So, f(x) = b is called a. The function f(x) = 0 is called the. Example #2: Constant Function Graph g ( x) = 3. First make a table of values. Another special case of slope-intercept form is,. This is the function. The graph is the line through the with slope 1. Since the function does not change the input value, is called the. Absolute Value and Piecewise Functions Another special function is the,. 7
The absolute value function can be written as. A function that is written using two or more is called a. Recall that a family of graphs is a group of graphs that displays one or more similar. The parent graph of most absolute value functions is. Example #3: Absolute Value Functions Graph f ( x) = x 3 and g ( x) = x + 2 on the same coordinate plane. Determine the similarities and differences in the two graphs. To graph other piecewise functions, examine the in the definition of the function to determine how much of each piece to include. Example #4: Piecewise Function x 1if x 3 Graph f ( x) =. 1if x > 3 Identify the domain and range. 8
Example #5: Identify Functions Determine whether each graph represents a step function, a constant function, an absolute value function, or a piecewise function. a) b) 9
Date: Algebra II 2 7: Graphing Inequalities Graph Linear Inequalities A linear inequality resembles a linear equation, but with an inequality symbol instead of an. For example, is a linear inequality and is the related linear equation. The graph of the inequality is the region. Every point in the shaded region satisfies the inequality. The graph of is the of the region. It is drawn as to show that points on the line satisfy the inequality. If the inequality symbol were < or >, then points on the boundary would not satisfy the inequality, so the boundary would be drawn as a You can graph an inequality by following these steps. Step 1 Determine whether the boundary should be or. Graph the boundary Step 2 Choose a not on the boundary and test the inequality. Step 3 If a inequality results, shade the region containing your test point. If a inequality results, shade the other region. Example #1: Dashed Boundary Graph x 2 y < 4. 10
Example #2: Solid Boundary Business A mail-order company is hiring temporary employees to help in their packing and shipping departments during their peak season. a) Write an inequality to describe the number of employees that can be assigned to each department if the company has 20 temporary employees available. b) Graph the inequality. c) Can the company assign 8 employees to packing and 10 employees to shipping? 11
Graph Absolute Value Inequalities Graphing absolute value inequalities is similar to graphing inequalities. The inequality symbol determines whether the boundary is or, and you can test a point to determine which region to. Example #3: Absolute Value Inequality Graph y x 2. 12