What focal length is needed for a 0.60x magnification with a diverging lens?

[Taylor Marks]

Homework Statement

What focus is needed for in order for a diverging lens to produce a magnification of 0.60x on an object located 1.40 meters away?

Homework Equations

M=hi/ho
1/do + 1/di = 1/f
M= -di/do

The Attempt at a Solution

-di / 1.4 = 0.6
1/1.4 + 1/.84 =1/f
-di=0.84
1.42

 

[ehild]

Homework Statement

What focus is needed for in order for a diverging lens to produce a magnification of 0.60x on an object located 1.40 meters away?

Homework Equations

M=hi/ho
1/do + 1/di = 1/f
M= -di/do

The Attempt at a Solution

-di / 1.4 = 0.6
1/1.4 + 1/.84 =1/f
-di=0.84
1.42

Is that + sign correct?

 

[andrevdh]

Just a small remark - rather say what focal length is needed...