If n=5 then 2*5=10, 10+3=13.
It’s 9. Square root is like the common factor of that number doubled by itself ... & 9x9 equals 81
Vertices are basically the corners, so for the triangle PQR, it would be the last option
This is because if you picture a triangle in your head, there are three vertices,for corners, which would be p, q and r