how to calculate distance euclidean

Hi guys I just cannot figure out the math behind how does these matrices produce this

c =

     1     5     6
     3     1     2
     0     4     5
     
     
a = {[1;5;2]}
b = {[2;6;7]}

c = pdist2(a{1},b{1},'euclidean')

Answer 1

[the cyclist]

c(m,n) is the absolute value of the difference between the m-th element of the vector stored in a and the n-th element of the vector stored in b.