Two points on a line are enough to find its slope, the change in for each -unit increase in . Put the change in over the change in , then type the fraction into Desmos. Subtract the points in the same order on top and bottom; switching the order on only one side flips the sign.
Hints
- Hint 1
The slope compares how much changes with how much changes. Put the change in on top. Which coordinates will you subtract on the bottom?
- Hint 2
Move from to . Subtract the first from the second , and the first from the second . Using the same order keeps the sign correct.
Step-by-step
Find the slope from the two points
Step 1Check whether the line rises or falls
From to , increases while decreases. The line falls as you move right, so its slope must be negative.
- Step 2
Set up the slope
Slope is the change in divided by the change in . Subtract the first point from the second in both places:
- Step 3
Evaluate and interpret the result
Type into Desmos. It prints : falls by while increases by , so the line's slope is . Choice A.