Wednesday, April 15, 2015

What point on the y-axis is 12sqrt13/13 units from the line defined by equation 3x -2y + 6 = 0?Answer: (0,-3) (0,9)

Given the equation of the
line:


3x - 2y + 6 = 0


We need
to find the point ( x,y) such that the distance between the line and the point is
12sqrt13


We will use thedistance between a point and a
line.


D = l ax + by + c l / sqrt(a^2 +
b^2)


==> 12sqrt13/ 13 = l 3x -2y + 6 l /
sqrt(9+4)


==> 12sqrt13 / 13 = l 3x-2y + 6 l /
sqrt13


Multiply and divide the right side by
sqrt13.


==> 12sqrt13 = l 3x-2y + 6l sqrt13/
13


==> l 3x -2y + 6 l =
12


==> But the point is on the y-axis, then x=
0


==> l -2y + 6 l =
12


Then, there are two
cases:


1) ==> -2y + 6 = 12 ==> -2y = 6
==> y= -3


2) ==> -(-2y+6) = 12 ==> 2y
= 18==> y= 9


Then the points are ( 0,
-3) and (0, 9) .

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