document.write( "Question 77475: For the function y= x2 - 6x + 8, put the function in the form y = a (x - h) squared + k. I was able to solve it by factoring and using the quadratic formula, but I can't figure out how to use this formula. \n" ); document.write( "
Algebra.Com's Answer #55591 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
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Solved by pluggable solver: Completing the Square to Get a Quadratic into Vertex Form

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\n" ); document.write( " \"y=1+x%5E2-6+x%2B8\" Start with the given equation
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\n" ); document.write( " \"y-8=1+x%5E2-6+x\" Subtract \"8\" from both sides
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\n" ); document.write( " \"y-8=1%28x%5E2-6x%29\" Factor out the leading coefficient \"1\"
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\n" ); document.write( " Take half of the x coefficient \"-6\" to get \"-3\" (ie \"%281%2F2%29%28-6%29=-3\").
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\n" ); document.write( " Now square \"-3\" to get \"9\" (ie \"%28-3%29%5E2=%28-3%29%28-3%29=9\")
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\n" ); document.write( " \"y-8=1%28x%5E2-6x%2B9-9%29\" Now add and subtract this value inside the parenthesis. Doing both the addition and subtraction of \"9\" does not change the equation
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\n" ); document.write( " \"y-8=1%28%28x-3%29%5E2-9%29\" Now factor \"x%5E2-6x%2B9\" to get \"%28x-3%29%5E2\"
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\n" ); document.write( " \"y-8=1%28x-3%29%5E2-1%289%29\" Distribute
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\n" ); document.write( " \"y-8=1%28x-3%29%5E2-9\" Multiply
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\n" ); document.write( " \"y=1%28x-3%29%5E2-9%2B8\" Now add \"8\" to both sides to isolate y
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\n" ); document.write( " \"y=1%28x-3%29%5E2-1\" Combine like terms
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\n" ); document.write( " Now the quadratic is in vertex form \"y=a%28x-h%29%5E2%2Bk\" where \"a=1\", \"h=3\", and \"k=-1\". Remember (h,k) is the vertex and \"a\" is the stretch/compression factor.
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\n" ); document.write( " Check:
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\n" ); document.write( " Notice if we graph the original equation \"y=1x%5E2-6x%2B8\" we get:
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\n" ); document.write( " \"graph%28500%2C500%2C-10%2C10%2C-10%2C10%2C1x%5E2-6x%2B8%29\" Graph of \"y=1x%5E2-6x%2B8\". Notice how the vertex is (\"3\",\"-1\").
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\n" ); document.write( " Notice if we graph the final equation \"y=1%28x-3%29%5E2-1\" we get:
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\n" ); document.write( " \"graph%28500%2C500%2C-10%2C10%2C-10%2C10%2C1%28x-3%29%5E2-1%29\" Graph of \"y=1%28x-3%29%5E2-1\". Notice how the vertex is also (\"3\",\"-1\").
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\n" ); document.write( " So if these two equations were graphed on the same coordinate plane, one would overlap another perfectly. So this visually verifies our answer.
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\n" ); document.write( "\n" ); document.write( "So the quadratic \"y=x%5E2+-+6x+%2B+8\" can be converted to the standard form \"y=a+%28x+-+h%29%5E2+%2B+k\" which is\r
\n" ); document.write( "\n" ); document.write( "\"y=%28x-3%29%5E2-1\" where a=1, h=3, and k=-1\r
\n" ); document.write( "\n" ); document.write( "Now we let y=0\r
\n" ); document.write( "\n" ); document.write( "\"0=%28x-3%29%5E2-1\"\r
\n" ); document.write( "\n" ); document.write( "\"1=%28x-3%29%5E2\" Add 1 to both sides\r
\n" ); document.write( "\n" ); document.write( "\"sqrt%281%29=sqrt%28%28x-3%29%5E2%29\"\r
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\n" ); document.write( "\n" ); document.write( "Which means \r
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\n" ); document.write( "\n" ); document.write( "\"x-3=1\" or \"x-3=-1\"\r
\n" ); document.write( "\n" ); document.write( "Now add 3 to both sides for each case to solve for x:\r
\n" ); document.write( "\n" ); document.write( "So our solutions are\r
\n" ); document.write( "\n" ); document.write( "\"x=4\" or \"x=2\"
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