document.write( "Question 459813: What is the width of a uniform expansion needed all around to double the area of a 10cm by 15cm rectangle \n" ); document.write( "

Algebra.Com's Answer #315328 by mananth(16946) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let x be the expansion on all sides.
\n" ); document.write( "length & width will increase by 2x\r
\n" ); document.write( "\n" ); document.write( "(10+2x)(15+2x)=300
\n" ); document.write( "150+20x+30x+4x^2=300
\n" ); document.write( "4x^2+50x+150=300
\n" ); document.write( "4x^2+50x-150=0
\n" ); document.write( "2x^2+25x-75=0\r
\n" ); document.write( "\n" ); document.write( "Find the roots of the equation by quadratic formula
\n" ); document.write( "
\n" ); document.write( "a= 2 ,b= 25 ,c= -75
\n" ); document.write( "
\n" ); document.write( "b^2-4ac= 625 - 600
\n" ); document.write( "b^2-4ac= 1225
\n" ); document.write( " $\"sqrt%28%091225%29\"$ =35
\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=(-25+ 35)/4
\n" ); document.write( "x1=2.5
\n" ); document.write( "x2=(-25 -35)/4
\n" ); document.write( "x2= -15
\n" ); document.write( "Ignore negative value
\n" ); document.write( "x=2.5 the expansion\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

\n" );