document.write( "Question 1137592: Please help with this question.
\n" ); document.write( "The demand function for a new DVD is p(x)=-2.5x+17.5 where p(x) represents the selling price, in thousands of dollars, and x is the number of DVDs sold, in thousands.
\n" ); document.write( "a) Determine the revenue function.
\n" ); document.write( "b) Determine the maximum revenue.
\n" ); document.write( "c) Determine the number of DVDs that need to be sold to reach the maximum revenue.
\n" ); document.write( "

Algebra.Com's Answer #755462 by MathLover1(20849)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "\"+p%28x%29=-2.5x%2B17.5\" where
\n" ); document.write( "\"p%28x%29\" represents the selling price, in thousands of dollars, and
\n" ); document.write( "\"x\" is the number of DVDs sold, in thousands. \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "a) Determine the revenue function.\r
\n" ); document.write( "\n" ); document.write( "\"+Revenue+=+Price+%2A+Quantity\"\r
\n" ); document.write( "\n" ); document.write( "\"R%28x%29=p%28x%29%2Ax\"\r
\n" ); document.write( "\n" ); document.write( "\"R%28x%29=%28-2.5x%2B17.5%29x\"\r
\n" ); document.write( "\n" ); document.write( "\"R%28x%29=-2.5x%5E2%2B17.5x\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "b) Determine the maximum revenue.\r
\n" ); document.write( "\n" ); document.write( "\"R%28x%29=-2.5x%5E2%2B17.5x\"............complete square to find \"vertex\", the vertex of a quadratic parabola is the highest or lowest point, the maximum or minimum \r
\n" ); document.write( "\n" ); document.write( "\"R%28x%29=-2.5%28x%5E2-7x%29\"\r
\n" ); document.write( "\n" ); document.write( "\"R%28x%29=-2.5%28x%5E2-7x%2Bb%5E2%29-%28-2.5%29b%5E2\"\r
\n" ); document.write( "\n" ); document.write( "\"R%28x%29=-2.5%28x%5E2-7x%2Bb%5E2%29%2B2.5b%5E2\"........\"b=7%2F2=3.5\"\r
\n" ); document.write( "\n" ); document.write( "\"R%28x%29=-2.5%28x%5E2-7x%2B3.5%5E2%29%2B2.5%2A3.5%5E2\"\r
\n" ); document.write( "\n" ); document.write( "\"R%28x%29=-2.5%28x-3.5%29%5E2%2B30.625\"\r
\n" ); document.write( "\n" ); document.write( "the maximum is at (\"3.5\",\"30.625\")\r
\n" ); document.write( "\n" ); document.write( "or, this way:\r
\n" ); document.write( "\n" ); document.write( "derivate \"R%28x%29\":\r
\n" ); document.write( "\n" ); document.write( "\"R%2Fdx=-2.5%2A2x%2B17.5\"\r
\n" ); document.write( "\n" ); document.write( "\"-5x%2B17.5=0\"\r
\n" ); document.write( "\n" ); document.write( "\"5x=17.5\"\r
\n" ); document.write( "\n" ); document.write( "\"x=3.5\"\r
\n" ); document.write( "\n" ); document.write( "find \"r%283.5%29\":\r
\n" ); document.write( "\n" ); document.write( "\"R%283.5%29=-2.5%2A3.5%5E2%2B17.5%2A3.5\"\r
\n" ); document.write( "\n" ); document.write( "\"R%283.5%29=-30.625%2B61.25\"\r
\n" ); document.write( "\n" ); document.write( "\"R%283.5%29=30.625\"->the \"maximum\" revenue \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "c) Determine the number of DVDs that need to be sold to reach the maximum revenue.
\n" ); document.write( "
\n" ); document.write( "since the maximum is at vertex (\"3.5\",\"30.625\"), the number of DVDs that need to be sold to reach the maximum revenue is \"x=3.5\"; so, in thousands, the number of DVDs that need to be sold to reach the maximum revenue is \"3500\" \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );