Personally, I think the people at the bottom just copied the answer again. I think your problem is: problem 1, you don't understand that a row vector multiplied by a column vector is a number. If you understand this problem, you have no problem; Question 2, you are not familiar with the operation (or you may forget it) [(KE+A) 2] T.

= [(KE+A)(KE+A)]^T

= (KE+A)^T(KE+A)^T

= [(KE+A)^T]^2

These steps are all finished with a t = a.