SOLUTION: is the relationship correct why or why not? √(x^2+y^2)=x+y

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Question 313735: is the relationship correct why or why not?
√(x^2+y^2)=x+y
Found 2 solutions by rapaljer, Alan3354:
Answer by rapaljer(4671) About Me  (Show Source):
You can put this solution on YOUR website!
NO!! You can't take the square root of TERMS, where there are additions or subtractions.

Dr. Robert J. Rapalje, Retired

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
sqrt%28x%5E2%2By%5E2%29+=+x+%2B+y
Square both sides
x%5E2+%2B+y%5E2+=+x%5E2+%2B+2xy+%2B+y%5E2
2xy = 0
The relationship is NOT true in general.
It's true only if x or y or both = zero (0).