1. Using Point-Slope Form to get SIF

2. y – y 1 = m (x – x 1 ) Write an equation given: (Goal: y = mx + b) A point and the slope. ◦ Use the point-slope form and simplify. Two points ◦ Calculate m. ◦ Follow the steps above using only ONE of the ordered pairs.

3. Example 1 Write an equation in SIF that passes through (2, -3) with a slope of ½. Answer: y= ½ x - 4

4. Example 2 Write an equation of a line that passes through (4, -2) and has a slope of 2. Answer: y = 2x - 10

5. Example 3 Write an equation of the line that passes through (-3, -1) and (6,-4). Answer: y = -1/3 x - 2

6. Example 4 Write an equation of the line that passes through (5,1) and (8, -2). Answer: y= -x +6

7. Example 5 Write an equation of the line whose slope is -2 and has an x-intercept of 3. Answer: y = -2x + 6

8. Use the equation to predict: In Chicago, a regular gallon of gasoline cost $2.05 in May and $2.42 in June. Write an equation to represent this situation. (Use January as month 1.) Answer: y = 0.37x +0.20

9. Now use it to predict If the Yellow Cab Company has budgeted $7000 for their July gas and they use, on average, 3000 gallons per month, will they have to increase their budget? ◦ y = 0.37x +0.20 ◦ Answer: The price of gas will be $2.79 in July. This means they will spend approx. $8370 in gas. They will need to increase their budget by $1370.