A magnifying glass always produces a virtual image larger in size than the object.
The image is virtual because, as shown in the diagram below, rays of light must be constructed to pass through the image.
This means that v is negative.
Because the lens is concave f is positive and u is positive because the object is real.
We can us the lens equation to find v, then the equation
to find the magnification. If f =10 and u =6 then
The magnification is given b
(ignoring signs).