The problem is given in the attachment below. The relevant information is provided under the "Stereo Audio" heading. Additionally, I have a couple of pieces of extra information not listed in the Stereo Audio section:
M is the component of (column vector) [R, L] on (column vector) [1, 1]
(This notation means that R and L are two entries in a column vector. The "R" being the upper entry and the "L" being the lower entry. The same applies for the 1 and 1)
D is the component of (column vector) [R, L] on (column vector) [-1, 1]
For the first problem, it asks me to express (M^2) + (D^2) in terms of L and R. Am I correct in writing (M^2) + (D^2) = [(L+R)^2]/4 +[(L-R)^2]/4?