Hey everyone! I have a question about the orthogonality of two vectors

The question is: It is given:llmll = 4;llnll = square root of 3;(m^,n)= 150 degrees(i) find the norm of the vector m + 2n

(ii) Determine if the vectors (m+2n) and (-m+n) are orthogonal

I got an answer of 2 for the norm but I don't know what to do for the second part. Do I just substitute the values of m and n into the vectors and if they both equal 0 when multiplied, they are orthogonal? Any help would be greatly appreciated