How to know if my laptop (DELL Vostro15 3546) will support DUAL RANK 2Rx 8GB RAM, it presently has 1Rx 4GB RAM. want to upgrade.

hi smart people, a quick help please..!

i have Dell Vostro 15_ 3546, it came with 1Rx 4GB RAM, i have checked via cmd prompt that it will support 8GB RAM.

I just want to know if there is any method to know if my laptop will support DUAL RANK 8 GB RAM.

On side notes, can anyone help me decide if i should fit an SSD first or go for RAM upgrade, as if i open few heavy apps the  system gets very slow in responding. I just want to know the priority with your reasoning to back it.

Thanks,

Gracias