I'm having a hard time with this question:

Question

"AB has endpoints A(n,4n) and B(3n,6n).
Which of the following is true?
A. AB=4n
B. The midpoint of AB is (2n,2n).
C. AB=n√8
D. The midpoint of AB is (4n,10n)".
PLEASE HELP!!!!!

Answer 1

AB = √(3n-n)^2+(6n-4n)^2 = √(4n^2+4n^2) = n√(8)
midpoint = (2n,5n)

looks like only C

Answer 2

Thanks!!!!