SOLUTION: if x plus y = a and xy = b, then the value of 1/x to the power of 3 plus 1/y to the power of 3 is equal to ?

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Question 935200: if x plus y = a and xy = b, then the value of 1/x to the power of 3 plus 1/y to the power of 3 is equal to ?
Found 3 solutions by josgarithmetic, MathLover1, Edwin McCravy:
Answer by josgarithmetic(39620)   (Show Source): You can put this solution on YOUR website!


, and one of your equations gives you xy=b, so you can substitute:

;

A formula is for the sum of cubes. You could try polynomial division to find it.
The formula in general:

Back to your expression,
, and you were given x+y=a;
.
Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!
if and , then
and
the value of
=
=
=
=
=

Answer by Edwin McCravy(20059)   (Show Source): You can put this solution on YOUR website!
The other two tutors above gave INCORRECT answers 
because they didn't know that you are not supposed 
to have x's and y's in the final answer, but only 
a's and b's.

if x plus y = a and xy = b, then the value of 1/x to the power of 3 plus 1/y to the power of 3 is equal to ?


 

Now we need to find .  We square both side of









So

 

answer:

 

Edwin
  

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