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beverton holt

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I tried to do a substitution with 2 equations but i got a really horrible quadratic with massive numbers and of course it didn't factorise but when i came to use the formula on it, it turned out the formula didn't work anyway.


How am i supposed to approach this question? The second part finding K and r
Original post by will'o'wisp2
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I tried to do a substitution with 2 equations but i got a really horrible quadratic with massive numbers and of course it didn't factorise but when i came to use the formula on it, it turned out the formula didn't work anyway.


How am i supposed to approach this question? The second part finding K and r


Given the answers are to 1 dec.pl, I wouldn't expect the quadratic to factorise.

I think it's just a case of ploughing through with the formula - which did work when I tried. I wasn't being careful, and there may be an error. I ended up with

15r2110r+104=015r^2-110r+104=0

Arithmetic slip somewhere?
Original post by ghostwalker
Given the answers are to 1 dec.pl, I wouldn't expect the quadratic to factorise.

I think it's just a case of ploughing through with the formula - which did work when I tried. I wasn't being careful, and there may be an error. I ended up with

15r2110r+104=015r^2-110r+104=0

Arithmetic slip somewhere?


hmm, let me try again i'll report back asap
Original post by ghostwalker
Given the answers are to 1 dec.pl, I wouldn't expect the quadratic to factorise.

I think it's just a case of ploughing through with the formula - which did work when I tried. I wasn't being careful, and there may be an error. I ended up with

15r2110r+104=015r^2-110r+104=0

Arithmetic slip somewhere?


man i get 24r2310+35124r^2 -310 +351

but nvm it's ok forget this one for now, i'll let it rest
Original post by will'o'wisp2
man i get 24r2310+35124r^2 -310 +351

but nvm it's ok forget this one for now, i'll let it rest


Just worked out a different route, avoiding the quadratic.

In order to avoid the subscripts, I'll use T for P_{n+1} and S for P_n

Our formula then becomes:

T=KrSK+(r1)S\displaystyle T=\frac{KrS}{K+(r-1)S}

Which after multplying up, and grouping the K terms together, gives:

(TrS)K=(1r)ST\displaystyle (T-rS)K = (1-r)ST

Plug in the two sets of values for S and T to get two equations, in K and r.

Then divide one equation by the other, eliminating K and the 1-r, and after multiplying up, you're left with a linear equation in r.
(edited 6 years ago)

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