DaNOOB said:

This is the link to the amazon page
https://www.amazon.com/Memory-Compatible-Aspire-5742-332G32Mnkk-As5552-N833G50Mnkk/dp/B00LICWEDK

As JackE says use reputable memory as these unknown memory modules could be problematic and might not work. Your Aspire 5742 has a HM55 chipset and OEM recommended RAM from Acer are those modules below, so the highest speed memory that I would go is the DDR3-1333MHz PC3-10600 which is one up from the max recommended specs for max memory performance.

Btw and as an example and from experience, I upgraded an Aspire 5750-2414 that has a different chipset of the HM65 (that's a higher spec and next model from your Aspire 5742) to 8GB (2x 4GB at DDR3-1600MHz at dual channel) that has a recommended Supports DIMM Speed of DDR3-1066Mhz or DDR3-1333MHz and it worked just fine, I also upgraded an Aspire V3-571G that has a H77 chipset and put 8GB 2x 4GB DDR3L-1866 PC3-14900 which also worked perfectly and in dual channel and was one up on the max recommended so that is the ratio that these laptops can be taken up to and upgraded to with memory to work the best, anyway good luck and hope this helps as these are the memory specs recommended by Acer for your 5742: