Do ethernet couplets slow down the connection?

I just bought a new computer and the wifi is really slow where I set it up. I want to get an ethernet cable but the distance from my computer to the router is approximately 50 feet. I don't want it to be like 3 feet too short if I get a 50 foot cable, so I want a 75 foot cable. I was thinking about buying 3 25 foot cables and using 2 couplers to connect them and get them to my computer. Will using the couplers make the connection any slower than if I just used one long cable?