Solve function giving [ ] result

[Rich]

Hello,

When trying to solve this equation i get a result of [], anyone else getting a similar result or perhaps can see an error in my method?

Trying to solve for x here:
348.4=269.65+.5*(315-269.65)+((x/26000)^2 + .25*(315-269.65)^2)^.5

I use the solve function:

solve('348.4=269.65+.5*(315-269.65)+((x/26000)^2 + .25*(315-269.65)^2)^.5', x)

and i get this result:
[]

Thanks