# Question about problem involving gcd

#### issacnewton

##### Member
Hello

I am studying the problem given in the attachement. In the solution given, it says "Similarly $$d|\gcd(a,-b)$$ ". I could not understand why this is so.

thanks

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#### caffeinemachine

##### Well-known member
MHB Math Scholar
Hello

I am studying the problem given in the attachement. In the solution given, it says "Similarly $$d|\gcd(a,-b)$$ ". I could not understand why this is so.

thanks
$d|\gcd(a,-b)$ follows from the fact that $d=\gcd(a,b)$.

#### issacnewton

##### Member
thanks...........I should have realised that......