Could someone please help me with this question

Prove Corollary 5.1.9: If f: D - R and if c is an accumulation point of D , then f can have only one limit at c . 1. by using Definition 5.1.1. ler fiD - RR and let c be an accumulation point of D. we say That a real number I is a limit off at c if for each Exo There exists a Sto such That If (x)- L/ CE whenever X ED and Oc/x-c C Question 3 with S, F C for all n, The sequence (f(S,)) converges To L. 20 pts 9 1 Theorem 4.1.14 If a sequence converges, its limit is unique