SOLUTION: Prove that if |x + y| = |x| + |y| then xy

SOLUTION: Prove that if |x + y| = |x| + |y| then xy > 0

Question 1195702: Prove that if |x + y| = |x| + |y| then xy > 0
Answer by ikleyn(52802) (Show Source): You can put this solution on YOUR website!
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Prove that if |x + y| = |x| + |y| then xy > 0
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This statement is INCORRECT, i.e. WRONG.

The counter-example is x= 0, y= 0.

Another counter-example is x= 0 and y is any real number.

Third counter-example is y= 0 and x is any real number.

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