document.write( "Question 123486: John used completing the square to find the zeros of the function y=9x^2-12x-33. Can someone please show please show me the steps for solving this ??? \n" ); document.write( "
Algebra.Com's Answer #90733 by ankor@dixie-net.com(22740)\"\" \"About 
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John used completing the square to find the zeros of the function
\n" ); document.write( "y = 9x^2 - 12x - 33
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\n" ); document.write( "Find the zeros:
\n" ); document.write( "9y^2 - 12x - 33 = 0
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\n" ); document.write( "When completing the square, y^2 has to have a coefficient of 1,
\n" ); document.write( "divide each term by 9:
\n" ); document.write( "y^2 - \"12%2F9\"x - \"33%2F9\" = 0
\n" ); document.write( ":
\n" ); document.write( "We are going to replace the 3rd term with a value that will make it a square
\n" ); document.write( "Add \"33%2F9\" to both sides:
\n" ); document.write( "y^2 - \"12%2F9\"x + ____ = \"33%2F9\"
\n" ); document.write( ":
\n" ); document.write( "We can determine the 3rd term as follows:
\n" ); document.write( "Divide the coefficient of x by 2; that would be \"6%2F9\"
\n" ); document.write( "Square this value; that would be \"36%2F81\" reduced to \"4%2F9\"
\n" ); document.write( ":
\n" ); document.write( "y^2 - \"12%2F9\"x + \"4%2F9\" = \"33%2F9\" + \"4%2F9\"; we have to add the same amt to both sides to keep an equation
\n" ); document.write( ":
\n" ); document.write( "y^2 - \"12%2F9\"x + \"4%2F9\" = \"37%2F9\";
\n" ); document.write( "Now it is a square, and can be factored to:
\n" ); document.write( "(y - \"2%2F3\") (y - \"2%2F3\") = \"37%2F9\"
\n" ); document.write( "or
\n" ); document.write( "(y - \"2%2F3\")^2 = \"37%2F9\"
\n" ); document.write( ":
\n" ); document.write( "Find the square root of both sides and we have;
\n" ); document.write( "y - \"2%2F3\" = +/-\"sqrt%2837%2F9%29%29\"
\n" ); document.write( ":
\n" ); document.write( "y = +\"2%2F3\" +/-\"sqrt%2837%2F9%29%29\" add 2/3 to both sides
\n" ); document.write( "We can factor 1/3 out of the radical, gets rid of the denominator inside the radical
\n" ); document.write( "y = \"2%2F3\" +/-\"%281%2F3%29sqrt%2837%29%29\"
\n" ); document.write( "or
\n" ); document.write( "y = \"%282+%2B+sqrt%2837%29%29%2F3\"
\n" ); document.write( "and
\n" ); document.write( "y = \"%282+-+sqrt%2837%29%29%2F3\"
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\n" ); document.write( "There are a lot of steps here. I hope you will take the time to study each one
\n" ); document.write( "If you have any questions, you can email me. Ankor
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