document.write( "Question 907680: Find a number t such that the distance between (-2,2) and (3t,2t) is as small as possible. \n" ); document.write( "
Algebra.Com's Answer #550542 by Fombitz(32388)\"\" \"About 
You can put this solution on YOUR website!
Use the distance formula.
\n" ); document.write( "\"D%5E2=%28-2-3t%29%5E2%2B%282-2t%29%5E2\"
\n" ); document.write( "\"D%5E2=%289t%5E2%2B12t%2B4%29%2B%284t%5E2-8t%2B4%29\"
\n" ); document.write( "\"D%5E2=13t%5E2%2B4t%2B8\"
\n" ); document.write( "To minimize the distance squared, take the derivative of the distance squared and set it equal to zero.
\n" ); document.write( "\"d%28D%5E2%29%2Fdt=26t%2B4%7D%7D%0D%0A%7B%7B%7B26t%2B4=0\"
\n" ); document.write( "\"26t=-4\"
\n" ); document.write( "\"t=-4%2F26\"
\n" ); document.write( "\"t=-2%2F13\"
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\n" ); document.write( "\n" ); document.write( "You could also do it geometrically.
\n" ); document.write( "(3t,2t) defines a line through the origin where \"y=%282%2F3%29x\"
\n" ); document.write( "You could find the line perpendicular to that line through the point (-2,2).
\n" ); document.write( "Perpendicular lines have negative reciprocal slopes so the slope would be \"m=-3%2F2\"
\n" ); document.write( "Using the point slope form of a line,
\n" ); document.write( "\"y-2=-%283%2F2%29%28x-%28-2%29%29\"
\n" ); document.write( "\"y-2=-%283%2F2%29x-3\"
\n" ); document.write( "\"y=-%283%2F2%29x-1\"
\n" ); document.write( "So then finding the intersection of the two lines,
\n" ); document.write( "\"%282%2F3%29x=-%283%2F2%29x-1\"
\n" ); document.write( "\"x%282%2F3%2B3%2F2%29=-1\"
\n" ); document.write( "\"x%2813%2F6%29=-1\"
\n" ); document.write( "\"x=-6%2F13\"
\n" ); document.write( "So then,
\n" ); document.write( "\"3t=-6%2F13\"
\n" ); document.write( "\"t=-2%2F13\"
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