Answer:
GCD(a,b) is multiple of d. It means d divides GCD(a,b).
Step-by-step explanation:
Let a and b are two unknown numbers.
If d divides a and d divides b, then a and b are multiple of d.
[tex]a=d\cdot m=dm[/tex]
[tex]b=d\cdot n=dn[/tex]
where, m and n are integers.
The greatest common divisor of a and b is
[tex]GCD(a,b)=d\cdot m\cdot n[/tex]
[tex]GCD(a,b)=d\cdot mn[/tex]
GCD(a,b) is multiple of d. It means d divides GCD(a,b).
Hence proved.