Write an equation in point-slope form for the line that passes through the given points (1,-3),(4,-15)

ANSWER: y= -4x+1
slope-intercept form is y=mx+b

to find m, which is the slope, we used
m=(y2-y1)/(x2-x1) (rise over run)
=(-15-(-3)/4-1)
= -12/3
= -4

to find b, choose one of the points and use the slope -4 and plug it in:
y=m(x)+b
-3= -4(1)+b
-3= -4+b
1=b