document.write( "Question 629012: if john's grandmother age is a perfect square, and her age equals the square of his father's age less the square of his mother's age, 40, what is the age of his grandmother?
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Algebra.Com's Answer #395975 by Edwin McCravy(20056)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "g = f² - 40²\r\n" );
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document.write( "factor the right side:\r\n" );
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document.write( "g = (f - 40)(f + 40)\r\n" );
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document.write( "f has to be older that 40; otherwise, (f - 40)(f + 40) would not be positive.\r\n" );
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document.write( "If f were 42 or older, the grandmother would be 164 or older, which nobody\r\n" );
document.write( "can be.  So the father can only be 41\r\n" );
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document.write( "g = (41 - 40)(41 + 40)\r\n" );
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document.write( "g = (1)(81)\r\n" );
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document.write( "g = 81\r\n" );
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document.write( "And that is a perfect square.  So the grandmother is 81.\r\n" );
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document.write( "Edwin
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