Question

A line has a slope of -2 and passes through the point (3, 1). What is the equation of this line in slope-intercept form?

a) y = -2x + 7

b) y = -2x + 5

c) y = 3x + 1

d) y = -2x - 4

Answer 1

Equation of line is y=mx + c 
where c is y-intercept and m is slope.

Sub (3,1) and slope into equation:
1 = -2(3) + c
1 = -6 + c
c = 7

Thus, equation is y = -2x + 7

Ans is (a)

Answer 2

ok well we know that the slope is -2 so that gets 1 out of the options, now you want to find the y value to get your last number well I will highly recommend you graph it so you know how to do it for a next time, you graph it by plugging the points they gave you adn using your slope figure it out, you plug in (3,1) and then rise 2 and run 1 toward the left side, because your slope is negative this gives you a y-intercept of 7 so your answer would be y=-2x+7, 

hope this helps