If we have Router A connected to 3 different networks and is using EIGRP
so what summary route will be shown in output of sh ip route on Router A
Yes. When you configure eigrp summary address of 172.16.5.128/26, it will have an entry in local RIB pointing to null interface.
If you want a single summary statement, the best one is this:
Just make sure there are no overlapping in any other part of the network.