document.write( "Question 147564: What does it mean to find the vertex, intercepts, and sketch of y=-x2-6x+1? \n" ); document.write( "
Algebra.Com's Answer #107950 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
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=-x%5E2-6x%2B1\", we can see that \"a=-1\", \"b=-6\", and \"c=1\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=%28-%28-6%29%29%2F%282%28-1%29%29\" Plug in \"a=-1\" and \"b=-6\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=%286%29%2F%282%28-1%29%29\" Negate \"-6\" to get \"6\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=%286%29%2F%28-2%29\" Multiply 2 and \"-1\" to get \"-2\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=-3\" Divide.\r
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\n" ); document.write( "\n" ); document.write( "So the x-coordinate of the vertex is \"x=-3\". Note: this means that the axis of symmetry is also \"x=-3\".\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=-x%5E2-6x%2B1\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-%28-3%29%5E2-6%28-3%29%2B1\" Plug in \"x=-3\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=-x%5E2-6x%2B1\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-%28-3%29%5E2-6%28-3%29%2B1\" Plug in \"x=-3\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=-1%289%29-6%28-3%29%2B1\" Square \"-3\" to get \"9\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=-9-6%28-3%29%2B1\" Multiply \"-1\" and \"9\" to get \"-9\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=-9%2B18%2B1\" Multiply \"-6\" and \"-3\" to get \"18\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=10\" Combine like terms.\r
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\n" ); document.write( "\n" ); document.write( "So the y-coordinate of the vertex is \"y=10\".\r
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\n" ); document.write( "\n" ); document.write( "So the vertex is .\r
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\r
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\n" ); document.write( "\n" ); document.write( "Intercepts:\r
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\n" ); document.write( "\n" ); document.write( "To find the y-intercept, simply plug in \"x=0\" and simplify.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-x%5E2-6x%2B1\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-%280%29%5E2-6%280%29%2B1\" Plug in \"x=0\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=-1%280%29-6%280%29%2B1\" Square \"0\" to get \"0\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=0-6%280%29%2B1\" Multiply \"-1\" and \"0\" to get \"0\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=0%2B0%2B1\" Multiply \"-6\" and \"0\" to get \"0\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=1\" Combine like terms.\r
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\n" ); document.write( "\n" ); document.write( "So when \"x=0\", \"y=1\". This means that the y-intercept is (0,1).\r
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\n" ); document.write( "\n" ); document.write( "X-intercept:\r
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\n" ); document.write( "\n" ); document.write( "To find the x-intercept, simply plug in \"y=0\" and solve for x.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-x%5E2-6x%2B1\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"0=-x%5E2-6x%2B1\" Plug in \"y=0\"\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-%28-6%29+%2B-+sqrt%28+%28-6%29%5E2-4%28-1%29%281%29+%29%29%2F%282%28-1%29%29\" Plug in \"a=-1\", \"b=-6\", and \"c=1\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+sqrt%28+%28-6%29%5E2-4%28-1%29%281%29+%29%29%2F%282%28-1%29%29\" Negate \"-6\" to get \"6\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+sqrt%28+36-4%28-1%29%281%29+%29%29%2F%282%28-1%29%29\" Square \"-6\" to get \"36\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+sqrt%28+36--4+%29%29%2F%282%28-1%29%29\" Multiply \"4%28-1%29%281%29\" to get \"-4\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+sqrt%28+36%2B4+%29%29%2F%282%28-1%29%29\" Rewrite \"sqrt%2836--4%29\" as \"sqrt%2836%2B4%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+sqrt%28+40+%29%29%2F%282%28-1%29%29\" Add \"36\" to \"4\" to get \"40\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+sqrt%28+40+%29%29%2F%28-2%29\" Multiply \"2\" and \"-1\" to get \"-2\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+2%2Asqrt%2810%29%29%2F%28-2%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+=+%286%29%2F%28-2%29+%2B-+%282%2Asqrt%2810%29%29%2F%28-2%29\" Break up the fraction. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+-3+%2B-+-1%2Asqrt%2810%29\" Reduce. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+-3-sqrt%2810%29\" or \"x+=+-3%2Bsqrt%2810%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "So our answers are \"x+=+-3-sqrt%2810%29\" or \"x+=+-3%2Bsqrt%2810%29\" \r
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\n" ); document.write( "\n" ); document.write( "which approximate to \"x=-6.162\" or \"x=0.162\" \r
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\n" ); document.write( "\n" ); document.write( "So the x-intercepts are roughly and \r
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\n" ); document.write( "\n" ); document.write( "With all of this info, we can now sketch the graph:\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+-x%5E2-6x%2B1%29+\" Graph of \"y=-x%5E2-6x%2B1\"
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