document.write( "Question 72977: please student in confusion....an object is projected upward from the top of tower. its distance in feet above the ground after t seconds is given by s(t)=-16t^2+64t+80. how many seconds will it take to reach ground. \n" ); document.write( "

Algebra.Com's Answer #52211 by funmath(2933) $\"\"$ $\"About$

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an object is projected upward from the top of tower. its distance in feet above the ground after t seconds is given by s(t)=-16t^2+64t+80. how many seconds will it take to reach ground.
\n" ); document.write( "It's height will be 0 when it hits the ground, so set the problem = to 0.
\n" ); document.write( " $\"0=-16t%5E2%2B64t%2B80\"$
\n" ); document.write( " $\"0=-16%28t%5E2-4t-5%29\"$
\n" ); document.write( " $\"0%2F-16=-16%28t%5E2-4t-5%29%2F-16\"$
\n" ); document.write( " $\"0=t%5E2-4t-5\"$ Factor
\n" ); document.write( " $\"0=%28t-5%29%28t%2B1%29\"$ set each factor = to 0 and solve for t.
\n" ); document.write( "t-5=0 or t+1=0
\n" ); document.write( "t-5+5=0+5 or t+1-1=0-1
\n" ); document.write( "t=5 or t=-1
\n" ); document.write( "Negative time is meaningless to us, so t=5 seconds.
\n" ); document.write( "Happy Calculating!!!!
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