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Question Number 190464 by alcohol last updated on 03/Apr/23

 { ((u_(n+1)  = u_n −3 )),((v_(n+1)  = 4v_n )) :} : u_0  = v_0  = 1  w_n  = ((1−u_n )/v_n )  − show that w_n  is bounded  − find a,b∈R such that a ≤ w_n  ≤ b

{un+1=un3vn+1=4vn:u0=v0=1wn=1unvnshowthatwnisboundedfinda,bRsuchthatawnb

Answered by mr W last updated on 03/Apr/23

u_0 =1  u_1 =1−3  u_2 =1−3×2  ...  u_n =1−3×n=1−3n    v_0 =1  v_1 =1×4  v_2 =1×4^2   ...  v_n =1×4^n =4^n   w_n =((1−(1−3n))/4^n )=((3n)/4^n )  lim_(n→∞) w_n =0  0≤w_n ≤(3/4)  for a≤w_n ≤b:   a=0, b=(3/4)

u0=1u1=13u2=13×2...un=13×n=13nv0=1v1=1×4v2=1×42...vn=1×4n=4nwn=1(13n)4n=3n4nlimnwn=00wn34forawnb:a=0,b=34

Commented by alcohol last updated on 03/Apr/23

alright thank you  what about the bounds?

alrightthankyouwhataboutthebounds?

Commented by mr W last updated on 03/Apr/23

i misread. w_n =((3n)/4^n ).

imisread.wn=3n4n.

Commented by alcohol last updated on 03/Apr/23

thank you  w_n  = ((3n)/4^n ) right ?  please how did you get ((3/4))^n ?

thankyouwn=3n4nright?pleasehowdidyouget(34)n?

Commented by mr W last updated on 03/Apr/23

w_0 =0=min  w_1 =(3/4)=max  0≤w_n ≤(3/4)

w0=0=minw1=34=max0wn34

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