Simplify the radical expression.

root of 56x^2

4x root of 14

is it 2x or 4x?

It is 4x.

on the answer list there is 2x root of 14, not a 4x root of 14.

Apologies for the confusion. The simplified form of the expression √(56x^2) is 2x√14. Thank you for pointing that out.