Why is the gfc of any two numbers is always even

Asequence of numbers begins with 12 and progresses geometrically. each number is the previous number divided by 2. which value can be used as the common ratio in an explicit formula that represents the sequence? 1/2 2 6 12

Ill mark the brainliest if you me with the these three questions 7,8,9

Which is the focus of a parabola with equation y2=4x