How do you add radicals ##sqrt10 + sqrt10##?

You can simply combine like terms and call it ##2sqrt10##.

Say I had ##x + x##. There are two ##x## terms, so we call it ##2x##, or two times ##x##. Say we let ##x = sqrt(10)## and had##sqrt(10) + sqrt(10)##. We would simply call it ##2sqrt(10)##.