Post Test: Coordinate Geometry

Select the correct answer.

Two points located on [tex]$\overleftrightarrow{JK}$[/tex] are [tex]$J(1,-4)$[/tex] and [tex]$K(-2,8)$[/tex]. What is the slope of [tex]$\overleftrightarrow{JK}$[/tex]?

A. -4
B. -2
C. [tex]$-\frac{1}{4}$[/tex]
D. [tex]$\frac{1}{4}$[/tex]
E. 4



Answer :

To find the slope of the line passing through the two points [tex]\( J(1, -4) \)[/tex] and [tex]\( K(-2, 8) \)[/tex], follow these steps:

1. Identify the coordinates of the two points:
- [tex]\( J(1, -4) \)[/tex]
- [tex]\( K(-2, 8) \)[/tex]

2. Recall the slope formula:
The slope [tex]\( m \)[/tex] between two points [tex]\((x_1, y_1)\)[/tex] and [tex]\((x_2, y_2)\)[/tex] is given by:
[tex]\[ m = \frac{y_2 - y_1}{x_2 - x_1} \][/tex]

3. Substitute the coordinates into the formula:
- Here, [tex]\( x_1 = 1 \)[/tex], [tex]\( y_1 = -4 \)[/tex], [tex]\( x_2 = -2 \)[/tex], and [tex]\( y_2 = 8 \)[/tex].

4. Calculate the difference in the y-coordinates (rise):
[tex]\[ y_2 - y_1 = 8 - (-4) = 8 + 4 = 12 \][/tex]

5. Calculate the difference in the x-coordinates (run):
[tex]\[ x_2 - x_1 = -2 - 1 = -3 \][/tex]

6. Find the slope by dividing the rise by the run:
[tex]\[ m = \frac{12}{-3} = -4 \][/tex]

Therefore, the slope of the line [tex]\(\overleftrightarrow{JK}\)[/tex] is [tex]\(-4\)[/tex].

So, the correct answer is:
A. -4