document.write( "Question 195718: A baseball player has hit a ball. The height, y, of the ball x seconds after it is hit is given by y= -16x^2 + 80x + 3.
\n" ); document.write( "At what time will the ball reach its maximum height? I used the quadratic formula and my answer was 2.04
\n" ); document.write( "What is the maximum height of the ball? I used the original formula.My answer was 232.78
\n" ); document.write( "When will the ball hit the ground? My answer was 4.08\r
\n" ); document.write( "\n" ); document.write( "Is this right??
\n" ); document.write( "thanks
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Algebra.Com's Answer #146754 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
At what time will the ball reach its maximum height?
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\n" ); document.write( "\n" ); document.write( "First, we need the vertex. The vertex will tell us what the max height will be:\r
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\n" ); document.write( "\n" ); document.write( "In order to find the vertex, we first need to find the x-coordinate of the vertex.\r
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\n" ); document.write( "\n" ); document.write( "To find the x-coordinate of the vertex, use this formula: \"x=%28-b%29%2F%282a%29\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=%28-b%29%2F%282a%29\" Start with the given formula.\r
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\n" ); document.write( "\n" ); document.write( "From \"y=-16x%5E2%2B80x%2B3\", we can see that \"a=-16\", \"b=80\", and \"c=3\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=%28-%2880%29%29%2F%282%28-16%29%29\" Plug in \"a=-16\" and \"b=80\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=%28-80%29%2F%28-32%29\" Multiply 2 and \"-16\" to get \"-32\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=5%2F2\" Reduce.\r
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\n" ); document.write( "\n" ); document.write( "So the x-coordinate of the vertex is \"x=5%2F2\". Note: this means that the axis of symmetry is also \"x=5%2F2\".\r
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\n" ); document.write( "\n" ); document.write( "Now that we know the x-coordinate of the vertex, we can use it to find the y-coordinate of the vertex.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-16x%5E2%2B80x%2B3\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-16%285%2F2%29%5E2%2B80%285%2F2%29%2B3\" Plug in \"x=5%2F2\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=-16%2825%2F4%29%2B80%285%2F2%29%2B3\" Square \"5%2F2\" to get \"25%2F4\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=-100%2B80%285%2F2%29%2B3\" Multiply \"-16\" and \"25%2F4\" to get \"-100\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=-100%2B200%2B3\" Multiply \"80\" and \"5%2F2\" to get \"200\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=103\" Combine like terms.\r
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\n" ); document.write( "\n" ); document.write( "So the y-coordinate of the vertex is \"y=103\".\r
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\n" ); document.write( "\n" ); document.write( "So the vertex is .\r
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\n" ); document.write( "\n" ); document.write( "which in decimal form is .\r
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\n" ); document.write( "\n" ); document.write( "So this means that at 2.5 seconds, the ball will be at the max height of 103.\r
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\n" ); document.write( "\n" ); document.write( "When will the ball hit the ground?\r
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\n" ); document.write( "\n" ); document.write( "\"y=+-16x%5E2+%2B+80x+%2B+3\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"0=+-16x%5E2+%2B+80x+%2B+3\" Plug in \"y=0\"\r
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\n" ); document.write( "\n" ); document.write( "Notice we have a quadratic equation in the form of \"0=ax%5E2%2Bbx%2Bc\" where \"a=-16\", \"b=80\", and \"c=3\"\r
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\n" ); document.write( "\n" ); document.write( "Let's use the quadratic formula to solve for x\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4ac+%29%29%2F%282a%29\" Start with the quadratic formula\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-%2880%29+%2B-+sqrt%28+%2880%29%5E2-4%28-16%29%283%29+%29%29%2F%282%28-16%29%29\" Plug in \"a=-16\", \"b=80\", and \"c=3\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-80+%2B-+sqrt%28+6400-4%28-16%29%283%29+%29%29%2F%282%28-16%29%29\" Square \"80\" to get \"6400\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-80+%2B-+sqrt%28+6400--192+%29%29%2F%282%28-16%29%29\" Multiply \"4%28-16%29%283%29\" to get \"-192\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-80+%2B-+sqrt%28+6400%2B192+%29%29%2F%282%28-16%29%29\" Rewrite \"sqrt%286400--192%29\" as \"sqrt%286400%2B192%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-80+%2B-+sqrt%28+6592+%29%29%2F%282%28-16%29%29\" Add \"6400\" to \"192\" to get \"6592\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-80+%2B-+sqrt%28+6592+%29%29%2F%28-32%29\" Multiply \"2\" and \"-16\" to get \"-32\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-80+%2B-+8%2Asqrt%28103%29%29%2F%28-32%29\" Simplify the square root (note: If you need help with simplifying square roots, check out this solver) \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-80%2B8%2Asqrt%28103%29%29%2F%28-32%29\" or \"x+=+%28-80-8%2Asqrt%28103%29%29%2F%28-32%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "So the possible answers are \"x+=+%28-80%2B8%2Asqrt%28103%29%29%2F%28-32%29\" or \"x+=+%28-80-8%2Asqrt%28103%29%29%2F%28-32%29\" \r
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\n" ); document.write( "\n" ); document.write( "which approximate to \"x=-0.037\" or \"x=5.037\" \r
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\n" ); document.write( "\n" ); document.write( "Since a negative time doesn't make sense, this means that the only solution is \"x=5.037\" \r
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\n" ); document.write( "\n" ); document.write( "So it will take about 5.037 seconds for the ball to hit the ground.\r
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