document.write( "Question 185459: Show by counterexample that (x+y)^-2 and x^-2+y^-2 are not equivalent. please help \n" ); document.write( "
Algebra.Com's Answer #139133 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Proof by Counterexample: \r
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\n" ); document.write( "\n" ); document.write( "Simply pick two random values for \"x\" and \"y\" and plug them in. I'm going to use \"x=1\" and \"y=1\" (these values are small and nonzero)\r
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\n" ); document.write( "\n" ); document.write( "\"%28x%2By%29%5E%28-2%29\" Start with the first expression.\r
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\n" ); document.write( "\n" ); document.write( "\"%281%2B1%29%5E%28-2%29\" Plug in \"x=1\" and \"y=1\"\r
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\n" ); document.write( "\n" ); document.write( "\"%282%29%5E%28-2%29\" Add\r
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\n" ); document.write( "\n" ); document.write( "\"1%2F%282%5E2%29\" Flip the fraction (to make the exponent positive)\r
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\n" ); document.write( "\n" ); document.write( "\"1%2F4\" Square \"2\" to get \"1%2F4\". \r
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\n" ); document.write( "\n" ); document.write( "So \"%28x%2By%29%5E%28-2%29=1%2F4\" when \"x=1\" and \"y=1\"\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E%28-2%29%2By%5E%28-2%29\" Move onto the second expression\r
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\n" ); document.write( "\n" ); document.write( "\"1%5E%28-2%29%2B1%5E%28-2%29\" Plug in \"x=1\" and \"y=1\" (note: these values cannot change now)\r
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\n" ); document.write( "\n" ); document.write( "\"1%2F1%5E2%2B1%2F1%5E2\" Flip the fractions (to make the exponents positive)\r
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\n" ); document.write( "\n" ); document.write( "\"1%2F1%2B1%2F1\" Square 1 to get 1\r
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\n" ); document.write( "\n" ); document.write( "\"1%2B1\" Reduce\r
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\n" ); document.write( "\n" ); document.write( "\"2\" Add\r
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\n" ); document.write( "\n" ); document.write( "So \"x%5E%28-2%29%2By%5E%28-2%29=2\" when \"x=1\" and \"y=1\"\r
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\n" ); document.write( "\n" ); document.write( "Since \"%28x%2By%29%5E%28-2%29=1%2F4\" and \"x%5E%28-2%29%2By%5E%28-2%29=2\" when \"x=1\" and \"y=1\", this means that \"%28x%2By%29%5E%28-2%29%3C%3Ex%5E%28-2%29%2By%5E%28-2%29\"
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