SOLUTION: Find two values of k such that the points (-3,4), (0,k), and (k,10) are collinear.

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Question 1010002: Find two values of k such that the points (-3,4), (0,k), and (k,10) are collinear.
Found 2 solutions by stanbon, MathLover1:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Find two values of k such that the points (-3,4), (0,k), and (k,10) are collinear.
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Look at the slopes::
1st point to 3rd point::
(k-4)/(0+3) = (10-4)/(k+3)
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Cross multiply::
k^2 - k - 12 = 3*6
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k^2 - k - 30 = 0
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(k-6)(k+5) = 0
k = 6 or k = -5
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Cheers,
Stan H.
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Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
Find two values of k such that the points (-3,4), (0,k), and (k,10) are collinear.
the points are collinear if they lie on same line
use the slope of a line to find k
slope+=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29
for the points (-3,4), (0,k),
slope+=%28k-4%29%2F%280-%28-3%29%29
slope+=%28k-4%29%2F%280%2B3%29
slope+=%28k-4%29%2F3.............eq.1
for (0,k), and (k,10)
slope+=%2810-k%29%2F%28k-0%29
slope+=%2810-k%29%2Fk ............eq.2
from eq.1 and eq.2 we have
%28k-4%29%2F3=%2810-k%29%2Fk............cross multiply
%28k-4%29%2Ak=3%2810-k%29
k%5E2-4k=30-3k
k%5E2-4k%2B3k-30=0
k%5E2-k-30=0...........factor completely
k%5E2-6k%2B5k-30=0
%28k%5E2-6k%29%2B%285k-30%29=0
k%28k-6%29%2B5%28k-6%29=0
%28k-6%29+%28k%2B5%29+=+0
solutions:
highlight%28k=6%29
highlight%28k=-5%29
so, the points (-3,4), (0,6), and (6,10) are collinear
and the points (-3,4), (0,-5), and (-5,10) are collinear
now find slope
slope+=%28k-4%29%2F3.............eq.1 if highlight%28k=6%29
slope+=%286-4%29%2F3
highlight%28slope+=2%2F3%29
slope+=%28k-4%29%2F3.............eq.1 if highlight%28k=-5%29
slope+=%28-5-4%29%2F3
slope+=-9%2F3
highlight%28slope+=-3%29
so, there are two possible lines and they are
highlight%28y=%282%2F3%29x%2Bb%29 and
highlight%28y=-3x%2Bb%29
we need y-intercepts b
y=%282%2F3%29x%2Bb use one point : (0,6)


6=%282%2F3%290%2Bb
b=6
y=%282%2F3%29x%2B6 and
y=-3x%2Bb use one point : (0,-5)
y=-3x-5
so, the line y=%282%2F3%29x%2B6 contains points the points (-3,4), (0,6), and (6,10)




and the line y=-3x-5 contains points the points (-3,4), (0,-5), and (-5,10)