M = -di/do
We can solve this equation for di:
di = -M × do
Substituting the given values:
di = -(1.5) × do = -1.5do
Now we can substitute both equations into the mirror equation and solve for do:
1/(-20 cm) = 1/do + 1/(-1.5do)
-0.05 = 1/do - 2/3do
-0.05 = (1 - 2/3)/do
-0.05 = 1/3do
do = -3/(0.05) = -60 cm
The negative sign indicates that the object (person's face) is located in front of the mirror, which is consistent with the fact that it is a concave mirror. Therefore, the person's face should be located 60 cm in front of the concave mirror in order to form an upright image that is magnified by a factor of 1.5.