Yes, that is the famous first Pythagorean triplet: 3²+4²=5²
or
For three lengths to be able to form a triangle, it suffices that every one of those lengths is shorter than the sum and longer than the difference of the other two.
It is enough to check just one side.
So,
3 + 4 > 5
4 - 3 < 5
Your triangle is constructible.
