slope formula is : (y2 - y1) / (x2 - x1)
set 1 : (0,0)...so we label them as : x1 = 0 and y1 = 0
set 2 : (-4,8)..so we label them as : x2 = -4 and y2 = 8
now we sub
slope = (8 - 0) / (-4 - 0) = -8/4 = -2
since it is going thru the origin, the y int is 0
in y = mx + b form, the slope will be in the m position and the y int will be in the b position
so ur equation is : y = -2x + 0, which is the same as y = -2x