document.write( "Question 79964: 50. A rock is thrown from the top of a tall building. The distance in feet, between the rock and the ground t seconds after it is thrown is given by d= -16t^2-2t+524. How long after the rock is thrown is it 321 feet from the ground?
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Algebra.Com's Answer #57418 by checkley75(3666) $\"\"$ $\"About$

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321=-16t^2-2t+524
\n" ); document.write( "-16t^2-2t+524-321=0
\n" ); document.write( "-16t^2-2t+203=0
\n" ); document.write( "using the quadratic equation we get:
\n" ); document.write( "t=(2+-sqrt[-2^2-4*-16*203])/2*-16
\n" ); document.write( "t=(2+-sqrt[4+12992])/-32
\n" ); document.write( "t=(2+-sqrt12996)/-32
\n" ); document.write( "t=(2+-114)/-32
\n" ); document.write( "t=(2+114)/-32
\n" ); document.write( "t=116/-32
\n" ); document.write( "t=-3.625 not the answer.
\n" ); document.write( "x=(2-114)/32
\n" ); document.write( "t=-112/-32
\n" ); document.write( "t=3.5 seconds is the answer.
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