What is the equation of this line in slope-intercept form?
a: y = 3x + 1
b: y=−1/3x−1
c: y=−3x−1
d: y=3x−1

The answer is C. 
It is C because Slope is the change in y over the change in x. From point 1, -4 it rose 6 and ran 2 which simplifies to 3. (If you know the rise over run thing you will understand what I mean. BUT THE LINE IS GONG DOWN SO THE SLOPE IS NEGATIVE!)
Also -1 is the y-intercept because it crossed over the y axis, so A is already incorrect. D is incorrect because the slope is positive. And C is, well just wrong.

Hope this helps:)