Query about question "If$\sqrt{x+y}=4$, then $(x+y)^{\frac{2}{5}}$ is..." [145]

https://www.gregmat.com/problems/quant?problem=ifsqrtxy4-then-xyfrac25-is


interesting enough…if I do root five of 16 and then square it, there is a certainty that root five of 16 is less than 2, but is uncertain about if 1.(something) is larger than 2…

Can you explain further what you mean?