Test 2 Section 4 #28

There are a few ways to go here, but I think the easiest is just drawing the line and then using when you know about slope-intercept form to see which choice is the best fit. Just one thing: they’re trying to get you here with the sneaky axis labeling, so be careful. The coordinates of B and D are (–1, 6) and (3, –6), respectively.


There are those points graphed without all the rest of the diagram’s noise. There are three important things you can see without doing any calculating:

  • The slope is negative.
  • The slope is fairly steep (the line moves down faster than it moves right).
  • The y-intercept is positive.

All the answer choices have negative slopes, so the first thing isn’t all that helpful. The steepness eliminates choices C and D, though, and the positive y-intercept means the answer can’t be A, so it must be B, the only choice that doesn’t start off in slope-intercept form. Put B in that form to confirm:

y = –3(x – 1)
y = –3x + 3

Yep, that works! 🙂

(If it makes you feel better, you can calculate the slope from the endpoints.) \text{slope}=\dfrac{y_2-y_1}{x_2-x_1}=\dfrac{-6-6}{3-(-1)}=\dfrac{-12}{4}=-3

Leave a Reply