document.write( "Question 322111: y = x^2 -2 is a function, but x = y^2 - 2 is not... can you say why?
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Algebra.Com's Answer #230582 by Edwin McCravy(20059) $\"\"$ $\"About$

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document.write( " is a function, \r\n" );
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document.write( "because no matter what value you substitute for x, there\r\n" );
document.write( "will be just one value for y.  The graph looks like this\r\n" );
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document.write( "It passes the vertical line test. That is,\r\n" );
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document.write( "when you pass vertical lines (the green one below):\r\n" );
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document.write( "none of those vertical intersects the graph more than once.\r\n" );
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document.write( "but  is not... can you say why?\r\n" );
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document.write( "Let's solve it for y:\r\n" );
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document.write( "The  tells us that when we substitute a\r\n" );
document.write( "value for x there will be two values for x, one with\r\n" );
document.write( "a + sign and one with a - sign.  For example when the\r\n" );
document.write( "single value 2 is substituted for x we get:\r\n" );
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document.write( "The graph looks like this\r\n" );
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document.write( "It does not pass the vertical line test, because\r\n" );
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document.write( "when you pass vertical lines (the green one below)\r\n" );
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document.write( "through the graph:\r\n" );
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document.write( "many of those vertical intersect the graph more than once.\r\n" );
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document.write( "Edwin

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