How to Prove Common Divisors Divide the G.C.D.?

[lifeonfire]

Homework Statement

Prove that for two integers m,n: all the common divisors divides the g.c.d.(m,n).

Homework Equations

The Attempt at a Solution

g.c.d = aA +bB ; where a, b are the integers

and let d be a common divisor, then:
d|a and d|b.

After this I have no clue where to go.

 

[VeeEight]

Do you know the formula for gcd involving lcm? Try using that.

 

[sachinism]

u can even try having a look at how gcd of 2 numbers is obtained http://en.wikipedia.org/wiki/Euclidean_algorithm"