Question help me choose a laptop memory

[oleannasert]

I have a laptop
HP Pavilion 15-R032TX (J8B78PA)
https://mobilespecs.net/laptop/HP/HP_Pavilion_15-R032TX_J8B78PA.html

I want to increase the laptop memory up to 8GB,
need a 4GB module, and the laptop allows me to do this, it has a free slot

 

[sdedu77]

On the official webpage (here) it states that it uses DDR3L memory. That "L" means that the module runs on 1.35V instead of the tipical 1.5V of DDR3.
Mixing different modules is not 100% guaranteed to work flawlessly.
For the best results, always get the same capacity, frequency and voltage. In your case, 4GB DDR3L, 1600mhz, 1.35V, (for laptops the module is also called SODIMM).