document.write( "Question 813725: a motorboat travels 9 mph in still water. It takes 5 hours longer to travel 55 miles going upstream than it does going downstream. Find the rate of the current. Hint (x+9) is going downstream and (x-9) is going upstream. round to nearest tenth. \r
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Algebra.Com's Answer #489909 by mananth(16946)\"\" \"About 
You can put this solution on YOUR website!
still water 9 mph
\n" ); document.write( "current - x mph\r
\n" ); document.write( "\n" ); document.write( "down stream = 9+x
\n" ); document.write( "upstream = 9-x\r
\n" ); document.write( "\n" ); document.write( "time upstream - time downstream = 5 hours\r
\n" ); document.write( "\n" ); document.write( "t=d/r\r
\n" ); document.write( "\n" ); document.write( "55/(9-x) -55/(9+x)=5\r
\n" ); document.write( "\n" ); document.write( "55(9+x)-55(9-x)=5(9^2-x^2)\r
\n" ); document.write( "\n" ); document.write( "495+55x-495+55x=405-5x^2\r
\n" ); document.write( "\n" ); document.write( "5x^2+110x-405=0\r
\n" ); document.write( "\n" ); document.write( "Find the roots of the equation by quadratic formula
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\n" ); document.write( "a= 5 , b= 110 , c= -405
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\n" ); document.write( "b^2-4ac= 12100 + 8100
\n" ); document.write( "b^2-4ac= 20200
\n" ); document.write( "\"%09sqrt%28%0920200%09%29=%09142.13%09\"
\n" ); document.write( "\"x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29\"
\n" ); document.write( "\"x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29\"
\n" ); document.write( "x1=( -110 + 142.13 )/ 10
\n" ); document.write( "x1= 3.21
\n" ); document.write( "\"x2=%28-b-sqrt%28b%5E2-4ac%29%29%2F%282a%29\"
\n" ); document.write( "x2=( -110 -142.13 ) / 10
\n" ); document.write( "x2= -25.21
\n" ); document.write( "Ignore negative value
\n" ); document.write( "current speed 3.2 mph
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