Can Lianjiayue E3572 desktop computer be replaced with 4G memory?

You can buy a 75 yuan with 1333 memory with DDR3 2G (it's better to be of the same brand, and you will know the brand after testing with Master Lu's hardware). As for your warranty, you can call Lenovo's after-sales service department first and ask about adding a memory. He will usually help you register, and your warranty is still valid.