Possible positions of object in magnified concave mirror?

[hds29ka]

Homework Statement

An object is magnified, by a factor; of 5, in a concave mirror. The mirror has a focal length of 20cm.
Calculate ALL possible positions of the object.

Homework Equations

M=Hi/Ho=Di/Do
M=V/U
1/F=1/V+1/U

The Attempt at a Solution

1/20=1/V + 1/U
-1U=20V/V
U=-20
V=10

 

[hds29ka]

Would I be correct?