Object Distance From Converging Lens for 1% Focal Length Difference

[spoonthrower]

How far away from a converging lens must an object be ( in terms of focal length, f ) so that the difference between the image distance and the focal lengh is 1% of the focal length?

I tried to translate the words into an equation based on the thin lens equation but i don't know if it is right or how to solve it for x in terms of f: tell me if I am right:

1/xf + 1/(f+.01f) = 1/f

please help! thanks.

 

[Chi Meson]

"Difference" means subtraction.

f-di=.01f so di=?

then, find do.

 

[andrevdh]

Seems right to me. You could also go the other way 0.99f.

 

[Chi Meson]

Oops. di will be greater than f, so you were right there. di=1.01f .

and do, call it "x" or "do" but not "xf"