document.write( "Question 775548: The height h in feet of an object after t seconds is given by the function:
\n" ); document.write( "h = –16t2 + 40t + 8. How long will it take the object to hit the ground? Round your answer to the nearest thousandth.
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Algebra.Com's Answer #472997 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"+h+=+-16t%5E2+%2B+40t+%2B+8+\"$
\n" ); document.write( "When the object hits the ground,
\n" ); document.write( " $\"+h+=+0+\"$
\n" ); document.write( " $\"+0+=+-16t%5E2+%2B+40t+%2B+8+\"$
\n" ); document.write( " $\"+-2t%5E2+%2B+5t+%2B+1+=+0+\"$
\n" ); document.write( " $\"+t+=+%28-b+%2B-+sqrt%28+b%5E2+-+4%2Aa%2Ac+%29%29+%2F+%282%2Aa%29+\"$
\n" ); document.write( " $\"+a+=+-2+\"$
\n" ); document.write( " $\"+b+=+5+\"$
\n" ); document.write( " $\"+c+=+1+\"$
\n" ); document.write( " $\"+t+=+%28-5+%2B-+sqrt%28+5%5E2+-+4%2A%28-2%29%2A1+%29%29+%2F+%282%2A%28-2%29%29+\"$
\n" ); document.write( " $\"+t+=+%28-5+%2B-+sqrt%28+25+%2B+8+%29%29+%2F+%28+-4+%29+\"$
\n" ); document.write( " $\"+t+=+%28-5+%2B-+sqrt%28+33+%29%29+%2F+%28+-4+%29+\"$
\n" ); document.write( " $\"+t+=+%28+-5+-+5.745+%29+%2F+%28-4%29+\"$
\n" ); document.write( "Note that I had to use the (-) square root to avoid
\n" ); document.write( "getting negative time
\n" ); document.write( " $\"+t+=+-10.745+%2F+%28-4%29+\"$
\n" ); document.write( " $\"+t+=+2.686+\"$
\n" ); document.write( "The object will hit
\n" ); document.write( "the ground in 2.686 sec
\n" ); document.write( "check answer:
\n" ); document.write( " $\"+-2t%5E2+%2B+5t+%2B+1+=+0+\"$
\n" ); document.write( " $\"+-2%2A+2.686%5E2+%2B+5%2A2.686+%2B+1+=+0+\"$
\n" ); document.write( " $\"+-2%2A7.215+%2B+13.43+%2B+1+=+0+\"$
\n" ); document.write( " $\"+-14.43+%2B+13.43+%2B+1+=+0+\"$
\n" ); document.write( " $\"+-14.43+%2B+14.43+=+0+\"$
\n" ); document.write( "OK\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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