Question 327203
a) Find the slope.
{{{m=(y2-y1)/(x2-x1)=(4-(-2))/(4-2)=6/2=3}}}
Now use the slope intercept form, {{{y=mx+b}}}
{{{y=3x+b}}}
and use either point to solve for b.
{{{4=3(4)+b}}}
{{{4=12+b}}}
{{{b=-8}}}
{{{highlight(y=3x-8)}}}
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{{{drawing(300,300,-10,10,-10,10,circle(0,-8,0.3),grid(1),circle(4,4,.3),circle(2,-2,.3),graph(300,300,-10,10,-10,10,3x-8))}}}
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Perpendicular lines have slopes that are negative reciprocals.
{{{m1*m2=-1}}}
{{{1*m2=-1}}}
{{{m2=-1}}}
{{{y=-x+b}}}
Use the point (0,8) to solve for b.
{{{8=0+b}}}
{{{b=8}}}
{{{highlight_green(y=-x+8)}}}
{{{drawing(300,300,-10,10,-10,10,circle(0,8,0.3),grid(1),graph(300,300,-10,10,-10,10,x+5,-x+8))}}}