Question 917809
Parallel lines have identical slopes. 
*[illustration TW.JPG].
Line 1 : {{{m=-5}}}
Line 2 : {{{(1/2)y=-x-4}}}
{{{y=-2x-8}}}
{{{m=-2}}}
Line 3 : {{{m=-2}}}
Line 4 : {{{m=-1/5}}}
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Line 2 and line 3 are parallel.
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{{{graph(300,300,-10,10,-10,10,-5x-5,-2x-8,-2x+4,-(x-9)/5-8)}}}
Line 1 : Red
Line 2 : Green
Line 3 : Blue
Line 4 : Purple