Ram mess

I bought a Maximus IV gene z (w/ i5 2500k and 2x2go of DDR3 Corsair Dominator) for my pc build from a guy for an amazing price. I was a little sceptic at first but he showed me the bios and all seemed ok (all was listed).

Now I would like to have at least 8go of ram on my system and I wanted to buy 2x2go corsair vengance . The only problem is that dominator are clocked at 1866Mhz and vengance at 1600Mhz.

Can I use them both on my system? And if yes , what do i have to do to get it to work?

Sorry for my English and yes, I'm quite a Ram Noob. ^^

Ps: Tr3x6g1866c9d ; 9-9-9-24 2 sticks is what he gave me exactly.

Thanks!

 

You can run them both but the dominators will be downclocked to 1600mhz.

Great ! Thanks for the quick answer!

The mobo will do it automatically? 

Yes, it will do it automatically but Pawmaniac is right, I had an old system that used different types of ram and it bluescreened all the time  so it's best to get another set of dominators.