Past exam of the mathematics course of the University of Cambridge / 2018 / ii / Paper 1 / 4G / a

The pumping lemma for context-free languages states that every context-free language $L$ has a pumping length $p$ such that every $w\in L$ with $|w|\ge p$ can be writtenwith $|vxy|\le p$, $|vy|>0$, and $u{v}^{i}x{y}^{i}z\in L$ for every integer $i\ge 0$.