document.write( "Question 1199211: Hello, can you please help me with this question? A ball is thrown upward with an initial speed of 19.6 m/s. When is the ball opposite a roof top that is 14.7 m high? Use the formula h = rt - 4.9t^2 where h is the height. \n" ); document.write( "

Algebra.Com's Answer #832961 by ikleyn(52781) $\"\"$ $\"About$

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document.write( "To find time \"t\", you need solve this quadratic equation\r\n" );
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document.write( "    -4.9t^2 + 19.6t = 14.7  meters.\r\n" );
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document.write( "Simplify it step by step\r\n" );
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document.write( "    -4.9t^2 + 19.6t - 14.7 = 0\r\n" );
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document.write( "Divide by (-4.9) both sides\r\n" );
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document.write( "    t^2 - 4t + 3 = 0\r\n" );
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document.write( "Factor left side\r\n" );
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document.write( "    (t-3)*(t-1) = 0.\r\n" );
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document.write( "There are two positive roots  t= 1 second and  t= 3 seconds.\r\n" );
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document.write( "First root is for the ball moving vertically up; the second root is for the ball falling down.\r\n" );
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\n" ); document.write( "\n" ); document.write( "Solved, with complete explanations.\r
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\n" ); document.write( "\n" ); document.write( "To see many other similar solved problems, look into the lessons\r
\n" ); document.write( "\n" ); document.write( "    - Problem on a projectile moving vertically up and down\r
\n" ); document.write( "\n" ); document.write( "    - Problem on an arrow shot vertically upward\r
\n" ); document.write( "\n" ); document.write( "    - Problem on a ball thrown vertically up from the top of a tower \r
\n" ); document.write( "\n" ); document.write( "    - Problem on a toy rocket launched vertically up from a tall platform\r
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