document.write( "Question 139347: Rita rows 12km upstream and 12 km downstream in 3 hours. The speed of her boat in still water is 9km/hour. Find the speed of the stream. \n" ); document.write( "
Algebra.Com's Answer #101605 by checkley77(12844)\"\" \"About 
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12/(9-X)+12/(9+X)=3
\n" ); document.write( "(12[9+X]+12[9-X])/(9-X)(9+X)=3
\n" ); document.write( "(108+12X+108-9X)/(81-X^2)=3 NOW CROSS MULTIPLY.
\n" ); document.write( "3(81-X^2)=108+12X+108-9X
\n" ); document.write( "243-3X^2=216+3X
\n" ); document.write( "-3X^2-3X+243-216=0
\n" ); document.write( "-3X^2-3X+27=0
\n" ); document.write( "-3(X^2+X-9)=0
\n" ); document.write( "USING THE QUADRATIC EQUATION WE GET:\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "X=(-1+-SQRT[1^1-4*1*-9])/2*1
\n" ); document.write( "X=(-1+-SQRT[1+36)/2
\n" ); document.write( "X=(-1+-SQRT37)/2
\n" ); document.write( "X=(-1+-6.083)/2
\n" ); document.write( "X=(-1+6.083)/2
\n" ); document.write( "X=5.083/2
\n" ); document.write( "X=2.54 ANSWER FOR THE SPEED OF THE CURRENT.
\n" ); document.write( "PROOF:
\n" ); document.write( "12/(9-2.54)+12/(9+2.54)=3
\n" ); document.write( "12/6.45+12/11.54=3
\n" ); document.write( "1.86+1.04=3
\n" ); document.write( "2.9~3
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