no, you can't - i would suggest to add 2 GB of the same modell - without any details
Please make sure to consider following points for ram upgrade
- generation - do you have DDR 2 / 3 / 4 ?
- laptop or pc - means SO-DIMM or LONG-Dimm
- speed - new one should match the same speed or better, as it clocks down automaticly...
- voltage - later notebooks just support low voltage dimms - for DDR3 it would be 1,5 V regular and 1,35 V lovo
last but not least, if you have first gen i-core CPU - most of current DDR3 4 GB modules will not work - you need a dual rank module, same for older intel atoms... please provide partnumbers of CPU, current RAM and your Mobo - so i cann tell you what to do, if you are not sure how to
okay, gigabyte is quite patient with mixed setup - i still would recommend to use 2 identical ram modules to benefit from dual-channel mode, which increases your performance...
if your budget supports, you might even consider 2*4 GB modules as new purchase - hard to judge - as your CPU will be even outperformed by any current intel i3... so if 8 GB would stress your buudget - add another 2 GB and save money for an intel system including new DDR4 :-/