document.write( "Question 1100705: A firework is launched off a building with an initial height of 152 ft, and an initial velocity off 481 ft/s. The firework will explode at 630 ft. How long after setting the firework off should the delay be set. Graph. \n" ); document.write( "

Algebra.Com's Answer #715291 by ikleyn(52879) $\"\"$ $\"About$

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\n" ); document.write( "A firework is launched off a building with an initial height of 152 ft, and an initial velocity off 481 ft/s.
\n" ); document.write( "The firework will explode at 630 ft. How long after setting the firework off should the delay be set. Graph.
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\n" ); document.write( "\n" ); document.write( "The post by @richwmiller is totally W R O N G. \r
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\n" ); document.write( "\n" ); document.write( "For your safety, simply ignore it.\r
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\n" ); document.write( "\n" ); document.write( "Below please find the correct solution.\r
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document.write( "The equation for the height (in feet) as a function of time in seconds is \r\n" );
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document.write( "h(t) = -16*t^2 + 481*t + 152.\r\n" );
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document.write( "The problem asks to find time moment/moments when h(t) = 630.\r\n" );
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document.write( "The equation takes the form\r\n" );
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document.write( "-16*t^2 + 481*t + 152 = 630  ====>\r\n" );
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document.write( "16*t^2 - 481*t + 630-152 = 0  ====>\r\n" );
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document.write( "16*t^2 - 481*t + 478 = 0\r\n" );
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document.write( "Use the quadratic formula\r\n" );
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document.write( " =  = .\r\n" );
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document.write( "There are TWO solutions:\r\n" );
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document.write( "1)   =  = 1.03 seconds on the ascending branch, and\r\n" );
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document.write( "2)   =  = 29.03 seconds on the descending branch.\r\n" );
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document.write( "Plot h(t) = -16*t^2 + 481*t + 152 (red) and y = 630 (green)\r\n" );
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