document.write( "Question 381486: Hi,\r
\n" ); document.write( "\n" ); document.write( "I have been trying to solve the below. I realise quadratic equations are involved but have only managed to get as far as 12[(1/x)+(1/x(x+7)]. Every time I try and get any further I get truely odd results! If you could please help. \r
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\n" ); document.write( "\n" ); document.write( "Charlotte\r
\n" ); document.write( "\n" ); document.write( "Bob takes seven hours longer than Norman to paint a house. If they work together, they can paint the house in 12 hours.
\n" ); document.write( "How long would it take each one of them, working alone, to paint the house? \n" ); document.write( "

Algebra.Com's Answer #270565 by ewatrrr(24785) $\"\"$ $\"About$

You can put this solution on YOUR website!


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document.write( "Hi,
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document.write( "Lettiing x and (x+7)represent the time it takes Norman and Bob alone to do the job.
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document.write( "Question States:  Per hour the Equalizer
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document.write( "  1/x + 1/(x+7) = 1/12  Multiplying each term by 12x(x+7) so as all denominators= 1
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document.write( " 12(x+7) + 12x = x(x+7)
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document.write( " 12x + 84 + 12x = x^2 + 7x
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document.write( " x^2 -17x - 84 = 0
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document.write( "factoring
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document.write( "(x-21)(x+4)= 0 
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document.write( " (x+4) = 0
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document.write( "    x = -4  tossing negative solution out
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document.write( " (x-21) = 0
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document.write( "    x = 21 hrs, time it takes Norman.  Bob 28hrs  ( 21+7)
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document.write( "CHECKING our Answer
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document.write( " 1/21 + 1/28 =  4/84 + 3/84 = 7/84 = 1/12 \n" );
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