Prove if a│b and a │c, then a│(b+c)?

Answer 1

if a|b then b=xa
if a|c then c=ya

then b+c=xa+ya or b+c=(x+y)*a
let x+y=z
thus (b+c)=za
thus a|(b+c)

Answer 2

Oh, that's better

a|b means a divides b so b=a*x for some x
a|c means c=a*y

b+c =??

got it?

Answer 3

This is the wrong category for home work assistance.