document.write( "Question 457154: An object launched upward with an initial velocity of 4.9 m/s from a height of 9.8 m will have a height of S(t)=-4.9t^2+4.9t+9.8, where S is in meters and t is in seconds.
\n" ); document.write( "a)how long will it take it to hit the ground?
\n" ); document.write( "b)Find the interval on which the height of the object is greater than 2.8m. \n" ); document.write( "
Algebra.Com's Answer #313818 by ankor@dixie-net.com(22740)\"\" \"About 
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An object launched upward with an initial velocity of 4.9 m/s from a height of
\n" ); document.write( " 9.8 m will have a height of S(t)=-4.9t^2+4.9t+9.8, where S is in meters and t is in seconds.
\n" ); document.write( ":
\n" ); document.write( "a)how long will it take it to hit the ground?
\n" ); document.write( "then S(t) = 0
\n" ); document.write( "-4.9t^2 + 4.9t + 9.8 = 0
\n" ); document.write( "we can simplify this, divide equation -4.9,
\n" ); document.write( "t^2 - t - 2 = 0
\n" ); document.write( "Factors easily to
\n" ); document.write( "(t-2)(t+1) = 0
\n" ); document.write( "positive solution
\n" ); document.write( "t = 2 seconds to hit the ground
\n" ); document.write( ":
\n" ); document.write( "b)Find the interval on which the height of the object is greater than 2.8m.
\n" ); document.write( "-4.9t^2 + 4.9t + 9.8 = 2.8
\n" ); document.write( "-4.9t^2 + 4.9t + 9.8 - 2.8 = 0
\n" ); document.write( "-4.9t^2 + 4.9t + 7 = 0
\n" ); document.write( "Use the quadratic formula to find t
\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "In this problem: x=t, a=-4.9, b=4.9, c=7
\n" ); document.write( "\"x+=+%28-4.9+%2B-+sqrt%284.9%5E2-4%2A-4.9%2A7+%29%29%2F%282%2A-4.9%29+\"
\n" ); document.write( "you can do the math here, the positive solution
\n" ); document.write( "t = 1.7956 sec
\n" ); document.write( "Interval above 2.8 m: 0 to < 1.7956 sec \n" ); document.write( "
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