Answer:
The fact that shows that p+q+r=1 is at most 2/3 is well explained from what we have below.
Step-by-step explanation:
Given that:
The maximum of function P = 2pq+2pr+2rq is at most 2/3.
where ;
p+q+r=1
From p+q+r=1
Let make r the subject ; then r = 1 - p - q
If we replace the value for r into the given function; we have:
P = 2pq+2pr+2rq
P = 2pq+2p(1 - p - q)+2(1 - p - q)q
P = 2pq + 2p - 2p² - 2pq + 2q -2pq -2q²
P = 2p - 2p² + 2q -2pq -2q²
By applying the standard method for determining critical points we obtain:
[tex]P_p[/tex] = -4p - 2q + 2 = 0
[tex]P_q[/tex] = -4q - 2p + 2 = 0
Divide all through by 2
[tex]P_p[/tex] = -2p - q + 1 = 0
[tex]P_q[/tex] = -2q - p + 1 = 0
[tex]P_p[/tex] = -2p - q = - 1
[tex]P_q[/tex] = -2q - p = - 1
Multiplying both sides by - ; we have:
[tex]P_p[/tex] = 2p + q = 1 ----- (1)
[tex]P_q[/tex] = 2q + p = 1 ------(2)
From equation (1) ; let make q the subject ; then
2p + q = 1
q = 1 - 2p
Now; let us replace the value of q = 1-2p into equation (2) , we have:
2q + p = 1
2(1-2p)+ p = 1
2 - 4p+p = 1
2 - 3p = 1
3p = 2-1
p = 1/3
Replacing the value of p = 1/3 into equation (1) ; we have :
2p + q = 1
2(1/3) + q = 1
2/3 + q = 1
q = 1 -2/3
q = 1/3
Taking the second derivative D; we have
[tex]D = P_{pp}P_{qq}-p^2_{pq}[/tex]
D = -4 × -4 - (2²)
D = 16 - 4
D = 12
This implies that the given function has a minimum or maximum at its critical point for which 12 > 0
Therefore , the value for function p = q = r since p, q, and r are the proportions of A, B, and O in the population.
Hence r = 1/3
P=2pq+2pr+2rq
P = 2(1/3)(1/3) + 2(1/3)(1/3) + 2(1/3)(1/3)
P = 6/9
P = 2/3
