document.write( "Question 985669: a.
\n" ); document.write( " $\"+12x+-+5x%5E2+\"$
\n" ); document.write( "What is the maximum value of this expression?\r
\n" ); document.write( "\n" ); document.write( "b.
\n" ); document.write( " $\"+y+=+4x%5E2+%2B+x+-+2+\"$
\n" ); document.write( "For which values of y will x be positive?\r
\n" ); document.write( "\n" ); document.write( "Please show working, thanks in advance \n" ); document.write( "

Algebra.Com's Answer #606499 by macston(5194) $\"\"$ $\"About$

You can put this solution on YOUR website!
a.
\n" ); document.write( " $\"y=12x-5x%5E2+\"$
\n" ); document.write( "Maximum occurs when first derivative=0
\n" ); document.write( " $\"dy%2Fdx=12-10x\"$ Set=0
\n" ); document.write( " $\"0=12-10x\"$
\n" ); document.write( " $\"10x=12\"$
\n" ); document.write( " $\"x=12%2F10\"$ = $\"6%2F5\"$ Maximum value when x=6/5.
\n" ); document.write( ".
\n" ); document.write( " $\"y=12x-5x%5E2\"$
\n" ); document.write( " $\"y=12%286%2F5%29-5%286%2F5%29%5E2\"$
\n" ); document.write( " $\"y=72%2F5-5%2836%2F25%29\"$
\n" ); document.write( " $\"y=360%2F25-180%2F25\"$ = $\"180%2F25=7.2\"$
\n" ); document.write( "ANSWER: Maximum value is 7.2.
\n" ); document.write( ".
\n" ); document.write( "Please limit to one question per post. \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

\n" );