document.write( "Question 763375: if x-y=-6 and xy=4, then find the value of x^3-y^3 \n" ); document.write( "
Algebra.Com's Answer #464795 by ankor@dixie-net.com(22740)\"\" \"About 
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if x-y=-6 and xy=4, then find the value of x^3-y^3
\n" ); document.write( "write it
\n" ); document.write( "x = y+6
\n" ); document.write( "replace x in the 2nd equation
\n" ); document.write( "y(y+6) = 4
\n" ); document.write( "y^2 + 6y - 4 = 0
\n" ); document.write( "using the quadratic formula, I got
\n" ); document.write( "y ~ -6.6
\n" ); document.write( "y ~ +.6
\n" ); document.write( "then
\n" ); document.write( "x = -.6
\n" ); document.write( "x = +6.6
\n" ); document.write( ":
\n" ); document.write( "using x = -.6; y = -6.6:
\n" ); document.write( "-.6^3 -(-6.6^3) =
\n" ); document.write( "-.216 + 287.496 = 287.28
\n" ); document.write( ":
\n" ); document.write( "Using x = 6.6; y = .6
\n" ); document.write( "287.496 - .216 = 287.28
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