Presentation on theme: "Warm up Graph the equation of the line using slope & y-intercept"— Presentation transcript:
1 Warm up Graph the equation of the line using slope & y-intercept 4x – 2y = 10
2 Lesson 8-5 Determining an Equation of a Line Objective: To find an equation of a line given the slope and one point on the line, or given two points on the line.
3 Finding the Equation of a Line If you know that the slope-intercept form of a line is y = mx + b then you can find the equation of any line if you know any 2 of the following:a) slopeb) y-interceptc) a point on the lined) x-intercept ( some point in which the y is 0) ( where the line crosses the x axis)
4 y = mx + bExample: if the slope is 4 and the y-intercept is -6 then the equation isy = 4x-6
5 Example 2Write the equation of a line that has a slope of - 3 and an x-intercept of 1/3.Solution: You can plug in the slope immediately so y = -3x + bThe x-intercept is just a point on the line where y is 0, so the point is (1/3,0)Any time you have a point you can plug it into the partial equation and then solve for the missing term. 0 = -3(1/3) + b
6 Now just solve for b so 0 = -1 +b Once you have b you can write the equationy = -3x + 1
7 Example 3Write the equation of the line passing through the points (1,1) and (2,4)Solution: If you have 2 point you can find the slope so 4-1 = 3 = 3then you can use one of the points the same way we used the x-intercept in example 2y = 3x + b (using (1,1)1 = 3(1) + b1 = 3 + b-2 = by = 3x -2 is the equation of the line
8 Practice Find the equation of the line when 1. slope is 2 and y-intercept is 152. slope is -3 and x-intercept -33. Line passes through the points (4, - 3), ( 3, -6)
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