document.write( "Question 1158945: An object is thrown upward at a speed of 91 feet per second by a machine from a height of 15 feet off the ground. The height h of the object after t seconds can be found using the equation h = − 16t^2 + 91t + 15\r
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Algebra.Com's Answer #781931 by ikleyn(52780) $\"\"$ $\"About$

You can put this solution on YOUR website!
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document.write( "(a)  It will happen, when h(t) = 102,  i.e.\r\n" );
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document.write( "     -16t^2 + 91t + 15 = 102.\r\n" );
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document.write( "     It is your basic equation to start.\r\n" );
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document.write( "     Solve it by any way you want.\r\n" );
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document.write( "     You will get 2 (two) roots.\r\n" );
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document.write( "     One root is the solution when the object moves up;  the other root is the solution, when the object falls down.\r\n" );
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document.write( "(b)  It will reach the ground, when h(t) = 0, i.e.\r\n" );
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document.write( "     -16t^2 + 91t + 15 = 0.\r\n" );
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document.write( "     So, this time you should solve this equation.\r\n" );
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