That is not possible on the 10 year old business computer with integrated video. 

Open Settings, System, Display to see what resolution is possible. The recommended setting is best. To open display settings quicker, right click on the Desktop. 

Thank you Mary for your reply. The best resolution offered by Settings is 1920 x 1080 which works well enough but an annoying error message about a mismatched display pops up too often and cannot be made to go away by clicking on any boxes. The processor is an i5-2400@3.1GHz

My other Dell with an i5-4460@3.2 GHz has no issue with the LG ultrawide monitors.

Just by mentioning CPU, I can tell your other Dell is newer than the 990.