2. Let an be the sequence defined inductively by a₁ = 2 and an+1 = 2 2 an + an (a) Prove by induction that an € [1, 2] for all n € N. (b) Prove that a ≥ 2 for all n € N. (c) Hence prove that the sequence is decreasing. (d) We already know that (an) is bounded below (by (a)) so it follows, by the mono- tone convergence theorem, that (an) converges to some limit L. Show that L> 0 and L² = 2.

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
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2. Let an be the sequence defined inductively by a₁ = 2 and an+1 =
(a) Prove by induction that an € [1, 2] for all n € N.
(b) Prove that a ≥2 for all ne N.
an +
an
(c) Hence prove that the sequence is decreasing.
(d) We already know that (an) is bounded below (by (a)) so it follows, by the mono-
tone convergence theorem, that (an) converges to some limit L. Show that L>0
and L² = 2.
Transcribed Image Text:1 2. Let an be the sequence defined inductively by a₁ = 2 and an+1 = (a) Prove by induction that an € [1, 2] for all n € N. (b) Prove that a ≥2 for all ne N. an + an (c) Hence prove that the sequence is decreasing. (d) We already know that (an) is bounded below (by (a)) so it follows, by the mono- tone convergence theorem, that (an) converges to some limit L. Show that L>0 and L² = 2.
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