Is 192.168.9.64 26 a valid network address for IPv4?

Yeah it is!

Here is why

You have the subnet mask of 26 bits. So its becomes 255.255.255.192.

So the first three octets will be in the network address for sure. So we are done upto 192.168.9.x. In the last octet you have 2 bits on from the left, i.e.

128 64 32 16 8 4 2 1

1 1 0 0 0 0 0 0

You see that the bit corresponding to 64 is 1. That means it can come in the network address.:)