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October 23, 2014

October 23, 2014

Posted by **Jack** on Friday, May 11, 2007 at 9:04am.

Finding the shortest distance, to two decimal places, from the point P ( 7,5) to the line 2x+3y = 18?

Thanks

The square of the distance from a point on that line, at location x, is

D^2 = (7-x)^2 + (5-y)^2

= (7-x)^2 + [-1 + (2x/3)]^2

Set the derivative dD^2/dx = 0

Solve for x and then use the equation 2x+3y = 18 to get y. Then compute D

Another way to do this is to find the equation for the line through the point P that is perpendicular to the line. Since the slope of 2x+3y = 18 is -2/3, the slope of the perpendicular is 3/2.

another way would be to use vectors.

Have you studied vectors?

There is no point to show you the method unless you know the topic.

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