IIT JAM Follow
A. sara banu Asked a Question
July 30, 2021 11:36 am 15 pts
BOLZANO-WEIERSTRASS THEOREM Theorem: Every bounded sequence has a limit point. Proof: Let (a.) be a bounded sequence. Let S = {a,: n e N} be its range. Since the sequence is bounded, therefore, its range S is also bounded. Case I. Let S be a finite set. Then there must exist at least one element a e S such that a = a for an infinite number of values of n. For any 8> 0, the nbd. (a - 8, a + e) of a, contains a, o, for an infinite numb of n. Therefore, a is a limit point of (a,) Case II. Let S be an infinite set. The range S being an infinite bounded set has a limit point, say p, So each nbd( of p contains an infinite number of elements of S i.e. a, e (p E, p + 8) for an infinite number of values of n. Hence p is a limit point of (a, Remark An unbounded sequence may or may not have a limit point. Counter example, Since a, = n is an unbounded sequence with no limit point and even; a=n, if n is odd is an unbounded sequence with a limit point 1.
• 0 Likes
• 2 Shares
• Prerna chaudhary 1
https://youtu.be/0M8CkXmZtt4
A. sara banu
I don't know Hindi, I am tamil
• A. sara banu
can anyone xplain this theorem? 