Big Ideas Math Geometry, 2014
BI
Big Ideas Math Geometry, 2014 View details
2. Reflections
Continue to next subchapter

Exercise 32 Page 187

The segment connecting A and B has the shortest distance between them.

C(31/11,0)

Practice makes perfect

Let's begin by plotting the two given points.

Point C will be the point where the segment connecting points A and B intersects the x-axis.

Note that AB has the shortest distance between A and B. Therefore, the distance AC+BC is minimized. The point C lies on the x -axis so its y -coordinate is 0. Since we cannot exactly state its x -coordinate, we will find it algebraically. Note that a segment is a part of a linear function.

The slope of the line is - 116. With this in mind, we can write the equation of the line in slope-intercept form. y= -11/6x+ b To find the y-intercept b, we can substitute either the point A or the point B into the equation. Let's use A(-1,7).
y=-11/6x+b
7=-11/6( -1)+b
â–Ľ
Solve for b
7=11/6+b
7-11/6=b
42/6-11/6 =b
31/6=b
b=31/6
Now we can complete the equation of our line. y= -11/6x+ 31/6 We already know that the y -coordinate of the point C is 0. To find its x -coordinate, let's substitute y=0 in the above equation.
y=-11/6x+31/6
0=-11/6x+31/6
â–Ľ
Solve for x
-31/6=-11/6x
-31/6Ă· (-11/6)=x
-31/6*(-6/11)=x
31*6/6*11=x
31/11=x
x=31/11
We found that the exact coordinates of the point C are ( 3111,0).