- #1
roam
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Homework Statement
A sequence (an: [tex]n \in N[/tex]) is defined by an= (2n+3)/(3n+6) for all [tex]n \in N[/tex].
(a) Prove that this sequence is bounded above by 2/3;
(b) Prove that the sequence (an: [tex]n \in N[/tex]) is monotonely increasing by showing that 0<an+1-an for all [tex]n \in N[/tex].
The Attempt at a Solution
I need to write a perfect proof for this question, I made an attempt but I'm not sure if I'm using the right method and whether my proof is valid or makes any sense...
My attempt for part (a):
I want to use the method of induction. For this I need to show that (A) [tex]1 \in S[/tex], then (B) if a number [tex]n \in S[/tex] then so is the number after n.
If k is some natural number in the sequence, for k=1:
[tex]a_{n}=\frac{2.1+3}{3.1+6} = \frac{5}{9} \leq \frac{2}{3}[/tex]
Now, we have shown that [tex]a_{k} \leq \frac{2}{3}[/tex] and also premise A
ak+1 = (2.2+3)/(3.2+6)= 7/12 ≤ 2/3
Therefore an ≤ 2/3 for all [tex]n \in N[/tex].
I appreciate some guidance. Thank you.