Past exam of the year 1 of the computer science course of the University of Oxford / 2017 / Digital systems, linear algebra, introduction to formal proof / 5 / d / iii / Solution

Translate the mirror line to zero, reflect there, then translate back. Under the column-vector convention the rightmost operation acts first:This composition of affine transformations maps $(x,y)$ to $(4-x,y)$, fixing exactly the points with $x=2$.