Sequences/Series Help

I have been given a question as follows:

A sequence is given by x1 = 4, xn+1 = pxn-9

(1 is lower so is n+1, and n)

a.) show that x3 = 4p^2 -9p-9

b.) given that x3 = 46 find p

c.)Hence find the value of x5

I do not get part a and c, but had a go at p = 5,2.75 but it asks for a value not values.

Any help would be good, thanks

Reply 1

clareeey

13

Original post by Henwi

I have been given a question as follows:

A sequence is given by x1 = 4, xn+1 = pxn-9

(1 is lower so is n+1, and n)

a.) show that x3 = 4p^2 -9p-9

b.) given that x3 = 46 find p

c.)Hence find the value of x5

I do not get part a and c, but had a go at p = 5,2.75 but it asks for a value not values.

Any help would be good, thanks

Did you manage to find x2 okay?
Is there anything else in the question about the value of P?

(edited 5 years ago)

Reply 2

Henwi

OP

6

Someone explained to me the answer, but I have no clue to get x2, apparently it is 4p-9, but how?

Reply 3

clareeey

13

Original post by Henwi

Someone explained to me the answer, but I have no clue to get x2, apparently it is 4p-9, but how?

as you have an expression for x(n+1) which includes x(n) to get x(2) you substitute the value of x(1), 4 into the expression

Reply 4

username3093384

18

You get P as 5 and -2.75, I guess somewhere it says P>0, P is a positive constant or similar sentences. So use p = 5

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