document.write( "Question 200644: Find x if shaded area of a rectangle is 90(the whole rectangle is shaded except for the 3 holes). By developing and solving by factoring quadratic equation. The rectangle width is 2x-2, length is 3x, and there are 3 holes cut out with the width of x and length of x-1. \n" ); document.write( "
Algebra.Com's Answer #151098 by Earlsdon(6294)\"\" \"About 
You can put this solution on YOUR website!
I don't have a diagram of this situation but we can muddle through without one.
\n" ); document.write( "First, the big rectangle has an area of:
\n" ); document.write( "\"A%5B1%5D+=+%282x-2%29%283x%29\"
\n" ); document.write( "\"A%5B1%5D+=+6x%5E2-6x\" now we'll subtract the area of the three (\"3%28x%2A%28x-1%29%29\") rectangular holes whose total area is:
\n" ); document.write( "\"A%5B2%5D+=+3x%5E2-3x\" to get:
\n" ); document.write( "\"A%5B1%5D-A%5B2%5D+=+6x%5E2-6x-%283x%5E2-3x%29\"
\n" ); document.write( "\"A%5Bt%5D+=+3x%5E2-3x\" and this, the problem tells us is 90, so...
\n" ); document.write( "\"3x%5E2-3x+=+90\" Subtract 90 from both sides.
\n" ); document.write( "\"3x%5E2-3x-90+=+0\" Factor out a 3 to facilitate the calculation.
\n" ); document.write( "\"3%28x%5E2-x-30%29+=+0\" which means that...
\n" ); document.write( "\"x%5E2-x-30+=+0\" Factor this quadratic equation.
\n" ); document.write( "\"%28x%2B5%29%28x-6%29+=+0\" so...
\n" ); document.write( "\"highlight%28x+=+-5%29\" or \"highlight_green%28x+=+6%29\" Discard the negative solution as the length, x, can only be positive.
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