Question 320227
If the lines are parallel their slopes are identical.
{{{m=(y2-y1)/(x2-x1)=(0-y)/(1-7)=(4-1)/(4-(-2))=3/6=1/2}}}
{{{-y/-6=1/2}}}
{{{y=3}}}
.
.
.
{{{drawing(300,300,-10,10,-10,10,
circle(7,3,.3),
circle(1,0,.3),
circle(4,4,.3),
circle(-2,1,.3),
line(7,3,1,0),
line(4,4,-2,1),
grid(1),
graph(300,300,-10,10,-10,10,0))}}}