The equation of a line can be put in several different forms. The slope-intercept is one of those forms and it generically looks like y = mx + b where "m" is the slope and "b" is the y-intercept.
So we will be needing the slope. The slope is found using the slope equation:

where two points on the line are (x1, y1) and (x2, y2) so plugging in the points given to us (-4, 4) and (-3, 2), we get:
m = (2 - 4)/(-3 - -4) = (-2)/1 = -2
Now we can plug that value of "m" into y = mx + b to get y = -2x + b. The only thing left is to find the value of "b". Let's use one of the points given to us and plug it into "y = -2x + b" as an "x" and a "y". I'll pick the point (-4, 4). That gives us:
4 = -2(-4) + b
4 = 8 + b
-4 = b
So, plugging that value of "b" into y = -2x + b we get y = -2x - 4 which is our final answer.