I have used wireless extenders when pulling cable through walls, floors, and ceilings is impractical. But the extender is used to "extend" the effective range of the network - not replace it. And having then two separated by just 2.5m is not "extending" the range at all. In fact, being that close together could very well be degrading the range just has wifi range is often degraded in large apartment complexes due to multiple wifi signals "walking" all over each other.
For example, the extender would be placed 50 or more feet (15+ meters) away from the wireless router/WAP.