Are Relatively Prime Numbers Always Coprime?

bhavinsinh
I stumbled across this question:Suppose that a and b are relatively prime.Prove that ab and a+b are relatively prime.
 
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Use the fact that:
(a+b)/(ab)=1/b+1/a.
If I say more than this, then you wouldn't have anything to do for yourself.
 
Or you could assume that d|ab and prove that then d can't divide a+b (d=/=1).
 

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