document.write( "Question 1170723: A ball is hit into the air from a height of 4 feet. The function g(t)=-16t^2+120t+4 can be used to model the height of the ball where t is the time in seconds after the ball is hit.
\n" ); document.write( "a.About how long is the ball in the air?
\n" ); document.write( "b.When is the ball back to 4 feet off the ground?
\n" ); document.write( "c.How high is the ball after 4 seconds?
\n" ); document.write( "d.When is the ball 150 feet in the air?
\n" ); document.write( "e.What is the maximum height the ball reaches? How many seconds does it take for this max to occur?
\n" ); document.write( "

Algebra.Com's Answer #795604 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!
a. About how long is the ball in the air?\r
\n" ); document.write( "\n" ); document.write( "\"g%28t%29=0\"\r
\n" ); document.write( "\n" ); document.write( "\"0=-16t%5E2%2B120t%2B4\"\r
\n" ); document.write( "\n" ); document.write( "\"t=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F2a\"\r
\n" ); document.write( "\n" ); document.write( "\"t=%28-120%2B-sqrt%28120%5E2-4%28-16%294%29%29%2F%282%28-16%29%29\"....\r
\n" ); document.write( "\n" ); document.write( "\"t=%28-120%2B-sqrt%2814656%29%29%2F%28-32%29\"\r
\n" ); document.write( "\n" ); document.write( "\"t=%28-120%2B-121.06%29%2F%28-32%29\"\r
\n" ); document.write( "\n" ); document.write( "need only positive solution\r
\n" ); document.write( "\n" ); document.write( "\"t=%28-120-121.06%29%2F%28-32%29\"\r
\n" ); document.write( "\n" ); document.write( "\"t\"\"7.53\"seconds\r
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\n" ); document.write( "\n" ); document.write( "b. When is the ball back to \"4\" feet off the ground?\r
\n" ); document.write( "\n" ); document.write( "\"g%28t%29=4\"\r
\n" ); document.write( "\n" ); document.write( "\"4=-16t%5E2%2B120t%2B4\"....simplify\r
\n" ); document.write( "\n" ); document.write( "\"1=-4t%5E2%2B30t%2B1\"\r
\n" ); document.write( "\n" ); document.write( "\"0=-4t%5E2%2B30t%2B1-1\"\r
\n" ); document.write( "\n" ); document.write( "\"0=-4t%5E2%2B30t\"\r
\n" ); document.write( "\n" ); document.write( "\"0=-4t%28t-30%2F4%29\"\r
\n" ); document.write( "\n" ); document.write( "\"0=-4t%28t-15%2F2%29\"\r
\n" ); document.write( "\n" ); document.write( "need only positive solution\r
\n" ); document.write( "\n" ); document.write( "\"0=%28t-15%2F2%29\"\r
\n" ); document.write( "\n" ); document.write( "\"t=15%2F2\"\r
\n" ); document.write( "\n" ); document.write( "\"t=7.5\"seconds\r
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\n" ); document.write( "\n" ); document.write( "c. How high is the ball after \"4\" seconds?\r
\n" ); document.write( "\n" ); document.write( "\"t=4\"\r
\n" ); document.write( "\n" ); document.write( "\"g%284%29=-16%2A4%5E2%2B120%2A4%2B4\"\r
\n" ); document.write( "\n" ); document.write( "\"g%284%29=228\" feet\r
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\n" ); document.write( "\n" ); document.write( "d. When is the ball \"150\" feet in the air?\r
\n" ); document.write( "\n" ); document.write( "\"g%28t%29=150\"\r
\n" ); document.write( "\n" ); document.write( "\"150=-16t%5E2%2B120t%2B4\"\r
\n" ); document.write( "\n" ); document.write( "\"0=-16t%5E2%2B120t%2B4-150\"\r
\n" ); document.write( "\n" ); document.write( "\"0=-16t%5E2%2B120t-146\"\r
\n" ); document.write( "\n" ); document.write( "\"t=%28-120%2B-sqrt%28120%5E2-4%28-16%29%28-146%29%29%29%2F%282%28-16%29%29\"\r
\n" ); document.write( "\n" ); document.write( "\"t=%28-120%2B-sqrt%285056%29%29%2F%28-32%29\"\r
\n" ); document.write( "\n" ); document.write( "need only positive solution\r
\n" ); document.write( "\n" ); document.write( "\"t=%28-120%2B-71.1%29%2F%28-32%29\"\r
\n" ); document.write( "\n" ); document.write( "\"t=%28-120-71.1%29%2F%28-32%29\"\r
\n" ); document.write( "\n" ); document.write( "\"t=5.971875\"\r
\n" ); document.write( "\n" ); document.write( "\"t\"\"5.97\"seconds\r
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\n" ); document.write( "\n" ); document.write( "e. What is the maximum height the ball reaches? How many seconds does it take for this max to occur?\r
\n" ); document.write( "\n" ); document.write( "max is at vertex, write equation in vertex form\r
\n" ); document.write( "\n" ); document.write( "\"g%28x%29=-16t%5E2%2B120t%2B4\"....complete square\r
\n" ); document.write( "\n" ); document.write( "\"g%28x%29=%28-16t%5E2%2B120t%29%2B4\"\r
\n" ); document.write( "\n" ); document.write( "\"g%28x%29=-16%28t%5E2-%2815%2F2%29t%29%2B4\"\r
\n" ); document.write( "\n" ); document.write( "\"g%28x%29=-16%28t%5E2-%2815%2F2%29t%2Bb%5E2%29-%28-16b%5E2%29%2B4\".......\"b=%2815%2F2%29%2F2=15%2F4\"\r
\n" ); document.write( "\n" ); document.write( "\"g%28x%29=-16%28t%5E2-%2815%2F2%29t%2B%2815%2F4%29%5E2%29-%28-16%2815%2F4%29%5E2%29%2B4\"\r
\n" ); document.write( "\n" ); document.write( "\"g%28x%29=-16%28t-15%2F4%29%5E2%2B16%28225%2F16%29%2B4\"\r
\n" ); document.write( "\n" ); document.write( "\"g%28x%29=-16%28t-15%2F4%29%5E2%2B225%2B4\"\r
\n" ); document.write( "\n" ); document.write( "\"g%28x%29=-16%28t-15%2F4%29%5E2%2B229\"\r
\n" ); document.write( "\n" ); document.write( "=>\"h=15%2F4\" and \"k=229\"\r
\n" ); document.write( "\n" ); document.write( "vetex is at (\"15%2F4\",\"229\")\r
\n" ); document.write( "\n" ); document.write( "max is \"229\", and it will take \"15%2F4\" seconds for this max to occur\r
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