# Sequence in mathcad [closed]

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

Use Mathcad to determine the value of L45, giving your answer to 2 decimal places.

I am not sure how to use mathcad for this, so far i did this in mathcad

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## closed as off topic by Austin Mohr, Thomas, Chris Eagle, Norbert, tomaszOct 6 '12 at 11:49

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Let $$A=\begin{pmatrix} 2&-1.4\\1&0 \end{pmatrix}$$ and let
$$v_0=\begin{pmatrix} 0.1\\0.2 \end{pmatrix}$$ You will get the vector $$\begin{pmatrix} L_n\\L_{n-1} \end{pmatrix}$$ by multiplying $$\begin{pmatrix} L_{n-1}\\L_{n-2} \end{pmatrix}$$ by $A$. So you will want to multiply $v_0$ by a high power of $A$. The program is good at matrix manipulations.
Well, it is a linear recurrence with constant coefficients, but very different from the Fibonacci recurrence $F_n=F_{n-1}+F_{n-2}$. As to MathCad code, perhaps someone will supply it. There are also techniques from Linear Algebra for doing such computations fast, but that might take us too far afield. Certainly you could alternately just program the recurrence. –  André Nicolas Oct 3 '12 at 6:09