concave mirror radius

[Kris1120]

1. The problem statement, all variables and given/known data

A concave mirror has a focal length of
33.5 cm.
Determine the object position for which the
resulting image is upright and five times the
size of the subject.
Answer in units of cm.

2. Relevant equations

m=-(di/do)

(1/di)+(1/do)= 1/f

3. The attempt at a solution

1/do = (1/35) - (1/5) = -0.170149
do= -5.87719

[Redbelly98]

1/do = (1/35) - (1/5) = -0.170149

You're assuming di is 5 cm here, which isn't true.

[Kris1120]

I don't know how to solve for one without the other?

[Redbelly98]

You can write di in terms of do and m (using the magnification equation you had).

Then, substitute that for di in the "1/f=..." equation.