Question 872789
x-2y=4
and
4x-y=4
--
[ x-2y=4 ]
[ 8x-2y=8 ]


{{{8x-2y-(x-2y)=4}}}
{{{7x=4}}}
{{{x=4/7}}}
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{{{y=4x-4}}}
{{{y=4(4/7)-4}}}
{{{y=16/7-28/7}}}
{{{y=-12/7}}}
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Intersection point, (4/7,-12/7).


The line formed by the found point and the origin:
In this situation, y intercept is zero.
y=mx, and we can use slope formula to easily find slope; or we can see the slope from the found point.
From the origin, that point is found on the slope {{{-12/4=-3}}}.
(a) Answer is {{{highlight(y=-3x)}}}.


(b) is not much harder. Just that the slope will be different, and y-intercept will not be zero but something else.