SOLUTION: Please help me solve this: Find a number t such that the distance between (−3, 2) and (3t, 2t) is as small as possible

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Question 974087: Please help me solve this:
Find a number t such that the distance between
(−3, 2)
and
(3t, 2t)
is as small as possible

Found 2 solutions by Alan3354, Boreal:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Please help me solve this:
Find a number t such that the distance between
(−3, 2)
and
(3t, 2t)
is as small as possible
---------------------
d+=+sqrt%28%28-3+-+3t%29%5E2+%2B+%282+-+2t%29%5E2%29
d+=+sqrt%289+%2B+18t+%2B+9t%5E2+%2B+4+-+8t+%2B+4t%5E2%29
d+=+sqrt%2813t%5E2+%2B+10t+%2B+13%29
-----
dd/dt = %281%2F2%29%2A%2813t%5E2+%2B+10t+%2B+13%29%5E%28-1%2F2%29%2A%2826t%2B10%29
----
%2813t%5E2+%2B+10t+%2B+13%29%5E%28-1%2F2%29%2A%2813t%2B5%29+=+0
t = -5/13

Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
(-3,2) and (3t,2t)
need to minimize the squared deviations of (2t-2)^2 and (3t+3)^2
Take the first derivative and set it equal to zero.
2(2t-2)*2 + 2(3t+3)*3=0
8t-16 + 18t +18=0
26t+2=0
t=(-1/13)
(-3,2), (-3/13,-2/13)

Distance is sqrt [(36/13)^2) + (28/13)^2 ]=sqrt (7.67+ 4.64)=3.51 units
Try 0 for t
(-3,2) and (0,0) ;;; distance sqrt (13)=3.61
The graph shows the line that the two points are on. The curve is the distance between the two points for various values of t. It is a minimum at (-2/13) for t. The distance from that minimum to the line is minimized.
graph%28300%2C300%2C-5%2C5%2C-2%2C40%2C13x%5E2%2B4x%2B13%2C%282%2F3%29x%29