What are all common factors of 4 and 8?

Answer 1

1, 2, 4

These are all common factors because they are all numbers that go into both 4 and 8.

For the number four: 1 x 4 , 2 x 2

For the number eight: 1 x 8 , 2 x 4

There are no other numbers that go into both 4 and 8 and so 1, 2 and 4 are the only common factors here