Find the matrix of the reflection in the line in that consists of all scalar multiples of the vector 5 6 .
Since your image is messed up lets do it for an arbitrary vector
So we need to know that transform of the basis vectors
First we need to project on the vector
Now to find the the direction vector we subtract
The above vector takes us from the tip of onto the line but we want to reflect across it so we need to multiply it by 2. This gives
Now just do the exact same thing with