document.write( "Question 1017466: If x + y = 7 and xy = 5, what is x^3 + y^3? \n" ); document.write( "

Algebra.Com's Answer #633765 by ikleyn(52756) $\"\"$ $\"About$

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\n" ); document.write( "If x + y = 7 and xy = 5, what is x^3 + y^3?
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document.write( "First let us make these equivalent transformations:\r\n" );
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document.write( " =  =  + .\r\n" );
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document.write( "So you have this identity:\r\n" );
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document.write( " =  + .\r\n" );
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document.write( "Now let us substitute the given values x + y = 7 and xy =5 into this identity. You will get\r\n" );
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document.write( " =  + 3*5*7.\r\n" );
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document.write( "Hence, \r\n" );
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document.write( " =  - 3*5*7 = 343 - 105 = 238.\r\n" );
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\n" ); document.write( "\n" ); document.write( "Closely related to this problem is the lesson HOW TO evaluate expressions involving x + 1/x, x^2 + 1/x^2 and x^3 + 1/x^3 in this site.\r
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