document.write( "Question 904102: Really need your help!
\n" ); document.write( "Height of a ball: If a ball is thrown directly upward with a velocity of 40 ft/s, its height (in feet) after t seconds is given by y = 40t - 16t^2. What is the maximum height attained by the ball?
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Algebra.Com's Answer #548538 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
The given formula is a parabola with a vertex
\n" ); document.write( "that is a maximum. Here's a plot:
\n" ); document.write( "\"+graph%28+400%2C+400%2C+-1%2C+4%2C+-10%2C+30%2C+-16x%5E2+%2B+40x+%29+\"
\n" ); document.write( "--------------------
\n" ); document.write( "When the parabola has the form:
\n" ); document.write( "\"+a%2Ax%5E2+%2B++b%2Ax+%2B+c+\", the x-coordinate of
\n" ); document.write( "the maximum is at:
\n" ); document.write( "\"+-b%2F%28+2a+%29+\"
\n" ); document.write( "\"+a+=+-16+\"
\n" ); document.write( "\"+b+=+40+\"
\n" ); document.write( "\"+-b%2F%282a%29+=+-40%2F%282%2A%28-16%29+%29+\"
\n" ); document.write( "\"+-b%2F%282a%29+=+40%2F32+\"
\n" ); document.write( "\"+40%2F32+=+5%2F4+\"
\n" ); document.write( "At \"+t+=+5%2F4+\", the height is a maximum
\n" ); document.write( "\"+y%5Bmax%5D+=+-16t%5E2+%2B+40t+\"
\n" ); document.write( "\"+y%5Bmax%5D+=+-16%2A%285%2F4%29%5E2+%2B+40%2A%285%2F4%29+\"
\n" ); document.write( "\"+y%5Bmax%5D+=+-16%2A%2825%2F16%29+%2B+50+\"
\n" ); document.write( "\"+y%5Bmax+%5D+=+50+-+25+\"
\n" ); document.write( "\"+y%5Bmax%5D+=+25+\" ft
\n" ); document.write( "This matches the plot\r
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