document.write( "Question 133089: Find the vertex and intercepts for h(x)= -x^2-2x+8 and sketch the graph? \n" ); document.write( "
Algebra.Com's Answer #97307 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( "To find the vertex, we first need to find the axis of symmetry (ie the x-coordinate of the vertex)\r
\n" ); document.write( "\n" ); document.write( "To find the axis of symmetry, use this formula:\r
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\n" ); document.write( "\n" ); document.write( "\"x=-b%2F%282a%29\"\r
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\n" ); document.write( "\n" ); document.write( "From the equation \"y=-x%5E2-2x%2B8\" we can see that a=-1 and b=-2\r
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\n" ); document.write( "\n" ); document.write( "\"x=%28--2%29%2F%282%2A-1%29\" Plug in b=-2 and a=-1\r
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\n" ); document.write( "\n" ); document.write( "\"x=2%2F%282%2A-1%29\" Negate -2 to get 2\r
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\n" ); document.write( "\n" ); document.write( "\"x=%282%29%2F-2\" Multiply 2 and -1 to get -2\r
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\n" ); document.write( "\n" ); document.write( "\"x=-1\" Reduce\r
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\n" ); document.write( "\n" ); document.write( "So the axis of symmetry is \"x=-1\"\r
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\n" ); document.write( "\n" ); document.write( "So the x-coordinate of the vertex is \"x=-1\". Lets plug this into the equation to find the y-coordinate of the vertex.\r
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\n" ); document.write( "\n" ); document.write( "Lets evaluate \"f%28-1%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%29=-x%5E2-2x%2B8\" Start with the given polynomial\r
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\n" ); document.write( "\n" ); document.write( "\"f%28-1%29=-%28-1%29%5E2-2%28-1%29%2B8\" Plug in \"x=-1\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28-1%29=-%281%29-2%28-1%29%2B8\" Raise -1 to the second power to get 1\r
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\n" ); document.write( "\n" ); document.write( "\"f%28-1%29=-%281%29--2%2B8\" Multiply 2 by -1 to get -2\r
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\n" ); document.write( "\n" ); document.write( "\"f%28-1%29=-1%2B2%2B8\" Negate any negatives\r
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\n" ); document.write( "\n" ); document.write( "\"f%28-1%29=9\" Now combine like terms\r
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\n" ); document.write( "\n" ); document.write( "So the vertex is (-1,9)\r
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\n" ); document.write( "\n" ); document.write( "Intercepts:\r
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\n" ); document.write( "\n" ); document.write( "Y-intercept:\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( "\"f%28x%29=-1x%5E2-2x%2B8\" Start with the given function\r
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\n" ); document.write( "\n" ); document.write( "\"f%280%29=-1%280%29%5E2-2%280%29%2B8\" Plug in \"x=0\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%280%29=-1%2A0-2%2A0%2B8\" Raise 0 to the 2nd power to get 0\r
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\n" ); document.write( "\n" ); document.write( "\"f%280%29=0-2%2A0%2B8\" Multiply -1 and 0 to get 0\r
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\n" ); document.write( "\n" ); document.write( "\"f%280%29=0-0%2B8\" Multiply 2 and 0 to get 0\r
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\n" ); document.write( "\n" ); document.write( "\"f%280%29=0%2B8\" Subtract 0 from 0 to get 0\r
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\n" ); document.write( "\n" ); document.write( "\"f%280%29=8\" Add 0 and 8 to get 8\r
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\n" ); document.write( "\n" ); document.write( "So when \"x=0\", we have \"y=8\" which means that the y-intercept is (0,8)\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, plug in y=0 and solve for x\r
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\n" ); document.write( "\n" ); document.write( "\"-x%5E2-2x%2B8=0\" Start with the given equation\r
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\n" ); document.write( "\n" ); document.write( "\"%28-x-4%29%28x-2%29=0\" Factor the left side (note: if you need help with factoring, check out this solver)\r
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\n" ); document.write( "\n" ); document.write( "Now set each factor equal to zero:\r
\n" ); document.write( "\n" ); document.write( "\"-x-4=0\" or \"x-2=0\" \r
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\n" ); document.write( "\n" ); document.write( "\"x=-4\" or \"x=2\" Now solve for x in each case\r
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\n" ); document.write( "\n" ); document.write( "So our answer is \r
\n" ); document.write( "\n" ); document.write( " \"x=-4\" or \"x=2\" \r
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\n" ); document.write( "\n" ); document.write( "which means that the x-intercepts are \r
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\n" ); document.write( "\n" ); document.write( "(-4,0) and (2,0)\r
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\n" ); document.write( "\n" ); document.write( "Notice if we graph \"y=-x%5E2-2x%2B8\", we can visually verify our answer\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%5E2-2x%2B8%29+\"
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