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Section 5- 4: Point-slope Form of a Linear Equation SPI 22C: select the graph that represents a given linear function. Objective: Graph and write linear equations in point-slope form. 3 Different Forms of a Linear Equation. 1. Slope-Intercept form: y = mx + b
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Section 5-4: Point-slope Form of a Linear EquationSPI 22C: select the graph that represents a given linear function Objective: Graph and write linear equations in point-slope form 3 Different Forms of a Linear Equation 1. Slope-Intercept form: y = mx + b 2. Standard Form: Ax + By = C 3. Point-Slope form: y – y1 = m (x – x1)
Point-Slope Form of a Linear Equation y – y1 = m ( x – x1) one set of ordered pair another set of ordered pair Slope of the linear equation
1 3 1 3 Graph a Linear Equation in Point-Slope Form y – y1 = m (x – x1) Graph the equation y – 2 = (x – 1). Step 1. Write the (x, y) ordered pair. (1, 2) Step 2. Write the slope (m). • Step 3. Graph the equation • plot ordered pair first • use slope from known point • draw solution line
Write a Linear Equation in Point-Slope Form Write the equation of a line with slope -3 that passes through the point (-1, 7). y – y1 = m (x – x1) y – = (x – ) -3 (-1) 7 Simplify y – 7 = -3(x + 1) What is the slope in the problem? -3 What is the point in the problem? (-1, 7)
Use Two Points to Write an Equation (Point-slope Form) Write an equation for the line in point-slope form. Step 1. Locate any two points (-1, 4) and (2, 3) Step 2. Use the points to find the slope Step 3. Use either point to write an equation. y – y1 = m (x – x1) Simplify
Write an Equation using a Table Is the relationship shown in the table linear? If so, model the data with an equation. Step 1. Find the rate of change of consecutive ordered pairs. (If the rate of change is the same, then the data is linear). 3 – (-1) = 4 6 – 4 = 2 7 – 6 = 1 5 – 3 = 2 10 – 7 = 3 11 – 5 = 6 Rate of Change Change in y Change in x 2 1 1 1 3 1 = = = 4 2 2 2 6 2 Rate of change is the same, so the data is linear
Continued . . . . Is the relationship shown in the table linear? If so, model the data with an equation. Step 2. Model the data with an equation Recall: Rate of change (slope) is ½ . y – y1 = m (x – x1) 1 y – = (x – ) 7 5 2 Use any ordered pair, from the table, to complete the equation
Real-world and Tables of Data The table at the right represents the amount of calories burned per day when working outdoors at the stated temperature. Is the relationship shown in the table linear? If so, model the data with an equation in point slope form. Step 1. Is the data linear? If so, what is the rate of change? Step 2. Write an equation in point-slope form. y – = (x – ) 3330 50