How to solve this sequence?

klian — Thu, 03 May 2018 15:06:46 GMT

A sequence Ln is such that L1 = 0.2, L2 = 0.1 andLn = 2Ln-1 - 1.5Ln-2 ( n >= 3 )Use Mathcad to determine the value of L43, giving your answer to 2 decimal places.Need help to input this into Mathcad as i am new to this software... Still trying to figure it out...

Re: How to solve this sequence?

StuartBruff — Tue, 22 Sep 2015 11:33:57 GMT

Kok Kiang Lian wrote:

A sequence Ln is such that L1 = 0.2, L2 = 0.1 and

Ln = 2Ln-1 - 1.5Ln-2 ( n >= 3 )

Use Mathcad to determine the value of L43, giving your answer to 2 decimal places.

Need help to input this into Mathcad as i am new to this software... Still trying to figure it out...

Please don't post the same question multiple times. It tends to lead to confusion and the people who are likely to answer will normally pick up your question ... of course, they may be busy or on holiday or ... 🙂

See my answer to your previous question here: Need help in using Mathcad

You need to look up range variables and how to enter array indices. Also look up the built-in variable ORIGIN that controls the value of the first index number of an array (0 by default)

Eg, for your problem, in a blank area of the worksheet just type ORIGIN, then a colon : , then 1 (because your problem starts with index 1, and you are new to Mathcad, you are better off setting ORIGIN to 1 rather than adjusting the indices to the standard 0-based ORIGIN values)

Next you'll need to create a range variable that will iterate over the indices. Note that Mathcad, unlike some applications, automatically creates new array elements if you give them a value, even if the index (or indices) lie outside the current range of the array. It is *very important* to understand the difference between range variables and vectors - the two may look the same if you evaluate them, but they are very different. A vector is a single data item that contains other values. A range variable is an implicit iterator - it holds what is sometimes referred to as a range or range definition (eg, 1,3..9) and not the values the definition represents (1,3,5,7,9).

To create the range variable type n, then the colon :, then 1 <something> 43. The <something> is a semicolon ; in Mathcad 15 or earlier and two fullstops .. in Mathcad Prime. You should see something like n:=1..43

the name L, then the open square bracket [, then n, then colon :, ,,, well that, plus my previous post, should be enough to get you going.

Type L then = to see all of the values of L. Type L [ k = to see the kth value of L

Stuart

Re: How to solve this sequence?

klian — Thu, 24 Sep 2015 07:24:48 GMT

Hi Sir,

Thanks for your help.

I got the Answer as -373.431. Think should be correct.

Regards,

Re: How to solve this sequence?

AlanStevens — Thu, 24 Sep 2015 07:43:22 GMT

Hmm! You might want to check your result.

Re: How to solve this sequence?

Werner_E — Thu, 24 Sep 2015 10:50:48 GMT

Thats the problem with double posts

-> Re: Need help in using Mathcad

topic How to solve this sequence? in Mathcad

How to solve this sequence?

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