1. The problem statement, all variables and given/known data An object and its lens-produced real image are 2.4 m apart. If the lens has 55-cm focal length, what are the possible values for the object distance? 2. Relevant equations 1/s+1/s'=1/f 3. The attempt at a solution The object and the image are 2.4m apart so I thought "Hey, that is the same as 240cm apart, cool." So now I have an image and an object that are 240cm apart and I thought, "well... that is basically the same as saying the image is either 240cm to the left of the object or 240cm to the right of the object. Since we dunno for sure we'll have to solve it both ways." At this point I'm thinking: s'=s-240 OR s'=s+240 So now I'm like "Sweet, lets plug that baby into the lens equation!" 1/s+(1/s-240)=1/55 OR 1/s+(1/s+240)=1/55 Then I flipped everything since it was all over one to make it easier on my eyeballs to see... s+2-240=55 OR s+s+240=55 Then I was all like "wham blam math mojo stuff" and finished with 295=s^2 OR -185=s^2 And then from their I thought I was wrong. So any help would be great, thanks!