Science talk:Math Exam Resources/Courses/MATH221/April 2013/Question 07 (b)

G = AffineGroup(2, QQ)

A = G.reflection([3,-4])

B = A.matrix()

print B

Without forgetting that B is an affine transformation and not linear (not sure if there is better code to use). Also, this requires Sage 5.11 or higher.