Give an example of a vector perpendicular to [6,2,3] that has the same length.

If the answer was [a,b,c]

a squared + b squared + c squared = 49

this is all i can get so far...

I know for [a,b] and [m,n] to be perpendicular am + bn =0

b/a X n/m = -1

bn = - am

am+bn = 0

Then, would this work for three numbers too?

[a,b,c,] and [ 6,2,3] 6a + 2b + 3c =0