SOLUTION: x+y=x×y=x²-y²

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Question 1062388: x+y=x×y=x²-y²
Answer by Edwin McCravy(20064) About Me  (Show Source):
You can put this solution on YOUR website!

x+y = x×y = x²-y²

Obviously x = 0 = y is a solution.

if x+y = x²-y² then

x%2By%22%22=%22%22x%5E2-y%5E2

x%2By%22%22=%22%22%28x-y%29%28x%2By%29

%28x%2By%29-%28x-y%29%28x%2By%29%22%22=%22%220

%28x%2By%29%281-%28x-y%29%5E%22%22%29%22%22=%22%220

%28x%2By%29%281-x%2By%29%22%22=%22%220

x%2By=0; 1-x%2By=0

y=-x;   y=x-1

But we have to make sure that

x%2By=xy

For the first case y=-x

x-x=x%28-x%29
0=x%5E2
0=x
y=-x
y=0

So one solution is x = y = 0, the obvious one.

------------------

For the second case y=x-1

y=x-1

x%2By=xy

x%2B%28x-1%29=x%28x-1%29

x%2Bx-1=x%5E2-x

2x-1=x%5E2-x

0=x%5E2-3x%2B1

x%5E2-3x%2B1=0

x+=+%28-%28-3%29+%2B-+sqrt%28%28-3%29%5E2-4%2A1%2A1+%29%29%2F%282%2A1%29+

x+=+%283+%2B-+sqrt%289-4%29%29%2F2+

x+=+%283+%2B-+sqrt%285%29%29%2F2+

y=x-1

For x+=+%283+%2B+sqrt%285%29%29%2F2+

y=+%283+%2B+sqrt%285%29%29%2F2-1

y=+%283+%2B+sqrt%285%29%29%2F2-2%2F2

y=+%281+%2B+sqrt%285%29%29%2F2

So a second solution is:

x+=+%283+%2B+sqrt%285%29%29%2F2+, y=+%281+%2B+sqrt%285%29%29%2F2 

----------------

For x+=+%283+-+sqrt%285%29%29%2F2+

y=+%283+-+sqrt%285%29%29%2F2-1

y=+%283+-+sqrt%285%29%29%2F2-2%2F2

y=+%281+-+sqrt%285%29%29%2F2

So a third solution is:

x+=+%283+-+sqrt%285%29%29%2F2+, y=+%281+-+sqrt%285%29%29%2F2 

Edwin