Simple beam deflection and center load

[roflpask]

Homework Statement

http://www.upload.ee/image/4762203/DSC_0009_1_.JPG
I need to find the formula which is in the red circle. Beam is simply supported at both ends and there is center load. Do you think that this is correct?

Homework Equations

The Attempt at a Solution

 

[pongo38]

Seems the right equation for flexural deflection, but, in addition, there could be a much smaller deflection due to shear.