Past exam of the mathematics course of the University of Cambridge / 2024 / iii / Paper 125 / 1 / b / i

Forthe negative of $(x,y)$ is $(x,-y-1)$. At $P=(0,1)$ the tangent slope isThe tangent is $y=1-4x/3$, so the addition formulas giveThusThe line through $P=(0,1)$ and $Q=(-2,1)$ is $y=1$. Its third intersection has $x=2$, and reflection under $y\mapsto -y-1$ gives