document.write( "Question 1139714: an object is thrown upward from the top of a 64 foot building with an initial velocity of 48 feet per second. the height h of the object after t seconds is given by the quadratic equation h= -16t^2+48t+64. When will the object hit the ground? \n" ); document.write( "

Algebra.Com's Answer #760222 by ikleyn(52776) $\"\"$ $\"About$

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document.write( "The object will hit the ground exactly and precisely at the time moment \"t\", when  h(t) = 0,  or, equivalently,\r\n" );
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document.write( "     = 0.\r\n" );
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document.write( "Simplify and solve for \"t\" :\r\n" );
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document.write( "     = 0\r\n" );
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document.write( "    (t-4)*(t+3) = 0.\r\n" );
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document.write( "The roots are t= 4  and  t= -3.  Only positive root  t= 4 is meaningful and provides the solution to the problem.\r\n" );
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document.write( "ANSWER.  In 4 seconds.\r\n" );
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