document.write( "Question 970736: a particle is projected from ground level so that its height above the ground after t second is given by 20 t-5t square meters. after how many seconds is it 15 meter above the ground? can you explain briefly why there are two possible answers? \n" ); document.write( "

Algebra.Com's Answer #593384 by macston(5194) $\"\"$ $\"About$

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\n" ); document.write( " $\"20t-5t%5E2=15\"$
\n" ); document.write( " $\"20t=5t%5E2%2B15\"$
\n" ); document.write( " $\"0=5t%5E2-20t%2B15\"$
\n" ); document.write( " $\"0=t%5E2-4t%2B3\"$
\n" ); document.write( " $\"0=%28t-3%29%28t-1%29\"$
\n" ); document.write( " $\"t-3=0\"$ $\"or\"$ $\"t-1=0\"$
\n" ); document.write( " $\"t=3\"$ $\"or\"$ $\"t=1\"$
\n" ); document.write( "ANSWER:
\n" ); document.write( "The particle reaches 15 meters on the way up after 1 second,
\n" ); document.write( "and passes 15 meters again after 3 seconds on the way down.
\n" ); document.write( " \n" ); document.write( "

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