Why can't I unistall these apps?

[Enbix]

I did a factory reset yesterday, then I downloaded a bunch of apps. I uninstalled some of them but 2 of them just won't go away, I unistall them and but they reappear after a while. They are DU Speed Booster and Google Alphabet Plugin.
They weren't there after the factory reset.
Is there a reason why they keep reappearin? Maybe a virus?

 

[Hamza Ahmad2]

Try using avast cleanup plugin.

 

[Enbix]

I tried it, didn't work