document.write( "Question 154223: For the function y = 3x^2 + 12x + 9 find:\r
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Algebra.Com's Answer #113530 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
y = 3x^2 + 12x + 9 ... Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "y' = 6x + 12 ... Find the first derivative\r
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\n" ); document.write( "\n" ); document.write( "y'' = 6 ... Find the second derivative \r
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\n" ); document.write( "\n" ); document.write( "Since y'' is always positive, this means that the function is concave up.\r
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\n" ); document.write( "\n" ); document.write( "Y-Intercept:\r
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\n" ); document.write( "\n" ); document.write( "\"y=3x%5E2+%2B+12x+%2B+9\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"y=3%280%29%5E2+%2B+12%280%29+%2B+9\" Plug in \"x=0\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=3%280%29%2B12%280%29%2B9\" Square \"0\" to get \"0\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=0%2B12%280%29%2B9\" Multiply \"3\" and \"0\" to get \"0\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=0%2B0%2B9\" Multiply \"12\" and \"0\" to get \"0\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=9\" Combine like terms.\r
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\n" ); document.write( "\n" ); document.write( "So the y-intercept is (0,9)\r
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\n" ); document.write( "\n" ); document.write( "X-Intercept(s):\r
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\n" ); document.write( "\n" ); document.write( "\"y=3x%5E2+%2B+12x+%2B+9\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"0=3x%5E2+%2B+12x+%2B+9\" 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 \"ax%5E2%2Bbx%2Bc\" where \"a=3\", \"b=12\", and \"c=9\"\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-%2812%29+%2B-+sqrt%28+%2812%29%5E2-4%283%29%289%29+%29%29%2F%282%283%29%29\" Plug in \"a=3\", \"b=12\", and \"c=9\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-12+%2B-+sqrt%28+144-4%283%29%289%29+%29%29%2F%282%283%29%29\" Square \"12\" to get \"144\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-12+%2B-+sqrt%28+144-108+%29%29%2F%282%283%29%29\" Multiply \"4%283%29%289%29\" to get \"108\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-12+%2B-+sqrt%28+36+%29%29%2F%282%283%29%29\" Subtract \"108\" from \"144\" to get \"36\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-12+%2B-+sqrt%28+36+%29%29%2F%286%29\" Multiply \"2\" and \"3\" to get \"6\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-12+%2B-+6%29%2F%286%29\" Take the square root of \"36\" to get \"6\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-12+%2B+6%29%2F%286%29\" or \"x+=+%28-12+-+6%29%2F%286%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-6%29%2F%286%29\" or \"x+=++%28-18%29%2F%286%29\" Combine like terms. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+-1\" or \"x+=+-3\" Simplify. \r
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\n" ); document.write( "\n" ); document.write( "So the answers are \"x+=+-1\" or \"x+=+-3\" \r
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\n" ); document.write( "So the x-intercepts are (-1,0) and (-3,0)\r
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\n" ); document.write( "\n" ); document.write( "Vertex:\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=3x%5E2%2B12x%2B9\", we can see that \"a=3\", \"b=12\", and \"c=9\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=%28-%2812%29%29%2F%282%283%29%29\" Plug in \"a=3\" and \"b=12\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=%28-12%29%2F%286%29\" Multiply 2 and \"3\" to get \"6\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=-2\" Divide.\r
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\n" ); document.write( "\n" ); document.write( "So the x-coordinate of the vertex is \"x=-2\". Note: this means that the axis of symmetry is also \"x=-2\".\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=3x%5E2%2B12x%2B9\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"y=3%28-2%29%5E2%2B12%28-2%29%2B9\" Plug in \"x=-2\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=3%284%29%2B12%28-2%29%2B9\" Square \"-2\" to get \"4\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=12%2B12%28-2%29%2B9\" Multiply \"3\" and \"4\" to get \"12\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=12-24%2B9\" Multiply \"12\" and \"-2\" to get \"-24\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=-3\" Combine like terms.\r
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\n" ); document.write( "\n" ); document.write( "So the y-coordinate of the vertex is \"y=-3\".\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( "Maximum or Minimum value:\r
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\n" ); document.write( "\n" ); document.write( "Since the function is concave up, this means that the function has a minimum. The max/min value correspond to the y coordinate of the vertex. So the minimum value is \"y=-3\"\r
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\n" ); document.write( "\n" ); document.write( "Here's a graph to verify our answers:\r
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\n" ); document.write( "\n" ); document.write( "\"+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+10%2C+3x%5E2%2B12x%2B9%29+\" Graph of \"y=3x%5E2%2B12x%2B9\"
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