The worst case performance for Quicksort comes

from the relation $T(n)=T(n-1)+n.$ You

want to use the substitution method to prove that

$T(n)=(n^2).$ Plugging in $C{n}^2$ :

the largest value of $C$ that doesn't work for the

$O(n^2)$ proof is

the largest value of $C$ that does work for the

$(n^2)$ proof is