Hello for this, you need to check out the company's specifications/matrix first, for compatibility. SFP+ for 25G and 10G look the same. This is just my personal opinion but the picture I'm expecting is, connecting fiber optic cable through 10G SFP +on the 25G port of the Dell switch you have, S5248.
Hi  I want to get suggestions on the cable and transceiver that can be used for the connection between DELL S5248F-ON and HP Procurve. The Dell is a 25G port and the HP is 10G port. copper or fiber optic?  
DELL TO HP PROCUVRE CONNECTION