document.write( "Question 211092: Alice throws a ball to Connor. The height, h (in meters) after time, t (in
\n" ); document.write( "seconds) is approximated by the formula h= 2 + 28t – 5t^2. Calculate the time
\n" ); document.write( "required for the ball to reach a height of 15m. \n" ); document.write( "
Algebra.Com's Answer #159493 by algebrapro18(249)\"\" \"About 
You can put this solution on YOUR website!
First you plug in the 15 into the equation which gives you 15 = 2 + 28t - 5t^2. Now all we have to do is solve for t. To start I suggest we get everything on the same side of the equation.
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\n" ); document.write( "\n" ); document.write( "15 = 2 + 28t - 5t^2
\n" ); document.write( "15-2-28t+5t^2 = 2-2 + 28t-28t-5t^2+5t^2
\n" ); document.write( "13-28t+5t^2 = 0
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\n" ); document.write( "\n" ); document.write( "Now lets just rearrange the equation so its in standard form.
\n" ); document.write( "5t^2-28t+13 = 0
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\n" ); document.write( "\n" ); document.write( "Now try as we might this equation won't factor evenly so we have to use the quadratic equation.
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\n" ); document.write( "\n" ); document.write( "\"t+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\" where a = 5, b = -28, and c = 13. Plugging in those values gives us:
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\n" ); document.write( "\n" ); document.write( "\"t+=+%2828+%2B-+sqrt%28+%28-28%29%5E2-4%2A5%2A13+%29%29%2F%282%2A5%29+\"
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\n" ); document.write( "\n" ); document.write( "Now we just simplify:
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\n" ); document.write( "\n" ); document.write( "\"t+=+%2828+%2B-+sqrt%28+%28-28%29%5E2-4%2A5%2A13+%29%29%2F%282%2A5%29+\"
\n" ); document.write( "\"t+=+%2828+%2B-+sqrt%28+784-260+%29%29%2F%2810%29+\"
\n" ); document.write( "\"t+=+%2828+%2B-+sqrt%28+524+%29%29%2F%2810%29+\"
\n" ); document.write( "\"t+=+%2828+%2B-+2%2Asqrt%28+131+%29%29%2F%2810%29+\"
\n" ); document.write( "\"t+=+%2814+%2B-+sqrt%28+131+%29%29%2F%285%29+\"
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\n" ); document.write( "\n" ); document.write( "Plugging this into our calculator we get answers of
\n" ); document.write( "t= 5.089104628 seconds or t = .510895 and I'm not sure which one we should use.\r
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