find the slope
the slope between the points (x1,y1) and (x2,y2) is (y2-y1)/(x2-x1)
(1,2) and (4,-4)
slope=(-4-2)/(4-1)=-6/3=-2
the equation of a line passing through (x1,y1) and having a slope of m is
y-y1=m(x-x1)
given
(1,2) AND SLOPE IS -2
y-2=-2(x-1)
convert to y=mx+b form and ax+by=c form
solve for y
y-2=-2x+2
add 2
y=2x+4
minus 2x both sides
-2x+y=4
times -1
2x-y=-4
equation is
y-2=-2(x-1) or
y+4=-2(x-4) or
y=-2x+4 or
2x-y=-4
