Question

What is radical 3 plus radical 4

Answer 1

The answer is 3.73205081 but the shorter version or your answer should be 3.732

Answer 2

Those two numbers can't be directly added as long as they're in
radical form.  The only way to add them is to find both square roots,
and then add those.

Another twist is the fact that every number has two square roots ...
one positive and the other negative.  So there are four possible sums
of (√3 + √4) .

√3 = + or - 1.732051  (rounded)

√4 = + or - 2 (exactly)

The four sums are:

(+1.73205) + (+2) =  3.732  (rounded)
(+1.73205) + (-2) = -0.268  (rounded)
(-1.73205) + (+2) = +0.268 (rounded)
(-1.73205) + (-2) = -3.732  (rounded)