Question

He unit circle has a radius of 1 unit and is centered at the origin. It is dilated so that it passes through the point (4, 0).

Answer 1

We know that

if the dilated circle passes through the point (4, 0)
so
the new radius is the distance from the origin to point (4,0)
d=√[(4-0)²+0²]-----> d=√16------> d=4 units

the new radius  is 4 units
original radius is 1 units

[new radius]=[scale]*[original radius]
scale=new radius/original radius-----> scale=4/1-----> 4

the answer is
the scale factor of dilation is 4