Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
7. Equations of Lines in the Coordinate Plane
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Exercise 57 Page 195

Practice makes perfect
a We have been given the vertices of a triangle as the following.
A(0,0), B(2,5), C(4,0) Let's plot the points and draw the triangle to have a better understanding.
In order to write an equation for the line that passes through the points A and B, we will first determine the slope of the line. We will use the formula to determine the Slope Formula. m=rise/run=y_2- y_1/x_2- x_1 In the formula, (x_1,y_1) and (x_2,y_2) are the points that are on the line. Let's apply the formula!
m = y_2-y_1/x_2-x_1
m=5- 0/2- 0
m=5/2
The slope of the line is 52. We also know that the y-intercept of the line is because it passes through A(0,0). Thus, we will write the equation in slope-intercept form. y=5/2x
b This time, we will write an equation of the line that passes through the points B and C in the same way.
m = y_2-y_1/x_2-x_1
m=0- 5/4- 2
m=-5/2

The slope of the line is - 52. This time, we will write the equation in point-slope form because we do not know its y-intercept. Let's use the point C as our point. y-0=-5/2(x-4) Let's distribute - 52 so that we have the equation in slope-intercept form. y=-5/2x+10

c The absolute value of the slopes are the same. However, one of the lines has a positive slope and the other has a negative slope. The y-intercept of the line from Part A is and the line from Part B is 10.