document.write( "Question 507830: Story Problem: One number is 2 more than 5 times the other. Their product is 24.\r
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document.write( "These are the formulas that I came up with for this story problem, but after substitution method I get the polynomial and get stumped on how to solve them.\r
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document.write( "xy=24
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document.write( "x=2+5y\r
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document.write( "(2+5y)y=24 5y^2 +2y=24 where do I go from here? \n" );
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Algebra.Com's Answer #340738 by oberobic(2304)![]() ![]() ![]() You can put this solution on YOUR website! x * y = 24 \n" ); document.write( "so \n" ); document.write( "x = 24/y \n" ); document.write( ". \n" ); document.write( "x = 5y + 2 \n" ); document.write( ". \n" ); document.write( "x=x \n" ); document.write( "so \n" ); document.write( "24/y = 5y + 2 \n" ); document.write( ". \n" ); document.write( "cross multiply \n" ); document.write( ". \n" ); document.write( "24 = y(5y + 2) \n" ); document.write( "24 = 5y^2 + 2y \n" ); document.write( ". \n" ); document.write( "5y^2 +2y - 24 = 0 \n" ); document.write( ". \n" ); document.write( "factor \n" ); document.write( ". \n" ); document.write( "(5y +12)(y - 2) = 0 \n" ); document.write( ". \n" ); document.write( "check the factoring with FOIL \n" ); document.write( ". \n" ); document.write( "5y^2 -10y +12y -24. \n" ); document.write( "OK \n" ); document.write( ". \n" ); document.write( "So, y = -12/5 or 2 \n" ); document.write( ". \n" ); document.write( "substitute to find x \n" ); document.write( ". \n" ); document.write( "x*y = 24 \n" ); document.write( "x*2 = 24 \n" ); document.write( "x = 12 \n" ); document.write( "OK \n" ); document.write( ". \n" ); document.write( "x*y = 24 \n" ); document.write( "x*-12/5 = 24 \n" ); document.write( "x = -10 \n" ); document.write( "OK \n" ); document.write( ". \n" ); document.write( "x = -10 when y = -12/5 \n" ); document.write( "x = 12 when y = 2 \n" ); document.write( ". \n" ); document.write( "Also check the other equation. \n" ); document.write( ". \n" ); document.write( "One number is 2 more than 5 times the other. \n" ); document.write( ". \n" ); document.write( "y = -12/5 \n" ); document.write( "x = 5y -2 \n" ); document.write( "x = 5*(-12/5) + 2 \n" ); document.write( "x = -12 + 2 \n" ); document.write( "x = -10 \n" ); document.write( "OK \n" ); document.write( ". \n" ); document.write( "y = 2 \n" ); document.write( "x = 5y +2 \n" ); document.write( "x = 10 + 2 \n" ); document.write( "x = 12 \n" ); document.write( "OK \n" ); document.write( ". \n" ); document.write( "So, we have two answers as shown above. \n" ); document.write( ". \n" ); document.write( "x = -10 when y = -12/5 \n" ); document.write( "x = 12 when y = 2 \n" ); document.write( ". \n" ); document.write( "These could be shown as ordered pairs: (-10,-12/5), (12,2) \n" ); document.write( "which suggests a graph. \n" ); document.write( ". \n" ); document.write( "x*y = 24 \n" ); document.write( "y = 24/x (red line in the following graph) \n" ); document.write( ". \n" ); document.write( "x = 5y + 2 \n" ); document.write( "5y = x -2 \n" ); document.write( "y = (1/5)x - 2/5 (blue line in the following graph) \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " |