document.write( "Question 978430: the length and width of a rectangle are (3x+1) and (2x-1)cm respectively.If the area of the rectangle is 144cm,find x
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Algebra.Com's Answer #599933 by KMST(5328)\"\" \"About 
You can put this solution on YOUR website!
\"%283x%2B1%29+%282x-1%29=144\"
\n" ); document.write( "\"6x%5E2-3x%2B2x-1=144\"
\n" ); document.write( "\"6x%5E2-x-1=144\"
\n" ); document.write( "\"6x%5E2-x-1-144=0\"
\n" ); document.write( "\"6x%5E2-x-145=0\"
\n" ); document.write( "We need to solve the quadratic equation above.
\n" ); document.write( "Quadratic equations can always be solved
\n" ); document.write( "by \"completing the square\"
\n" ); document.write( "and by applying the quadratic formula.
\n" ); document.write( "Some quadratic equations can also be solved by factoring,
\n" ); document.write( "and \"6x%5E2-x-145=0\" is one of those.
\n" ); document.write( "To factor, we look for factors of \"6%2A145\" .
\n" ); document.write( "No need to multiply, when we can find and recombine the prime factors:
\n" ); document.write( "\"6%2A145=%282%2A3%29%2A%285%2A29%29=%282%2A3%2A5%29%2A29=30%2A29\" ,
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\n" ); document.write( "So we can re-write \"6x%5E2-x-145=0\" as
\n" ); document.write( "\"%286x%2B29%29%28x-5%29=0\"--->\"system%286x%2B29=0%2C%22or%22%2Cx-5=0%29\" --->\"system%28x=-29%2F6%2C%22or%22%2Cx=5%29\" .
\n" ); document.write( "\"x=5\"--->\"system%282x-1=2%2A5-1=10-1=9%2C3x%2B1=3%2A5%2B1=15%2B1=16%29\" ,
\n" ); document.write( "for the length and width of the rectangle to be 16 and 9cm respectively,
\n" ); document.write( "which makes perfect sense, so \"highlight%28x=5%29\" is a good answer.
\n" ); document.write( "On the other hand,
\n" ); document.write( "\"x=-29%2F6\"---> ,
\n" ); document.write( "yielding negative numbers for the length and width of the rectangle, does not make sense.
\n" ); document.write( "So, \"x=-29%2F6\" is a solution for the equation \"%283x%2B1%29+%282x-1%29=144\" ,
\n" ); document.write( "but is not a solution to the word problem.
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