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The corner points of the bounded feasible region determined by a set of constraints in an LPP are P(0,5)P(0, 5), Q(3,5)Q(3, 5), R(5,0)R(5, 0) and S(4,1)S(4, 1). If the objective function is z=ax+2byz = ax + 2by, where, a,b>0a, b > 0, then the condition on aa and bb such that the maximum value of zz occurs at QQ and SS is

Solution

✅ Correct Option: 4

The Linear Programming Problem has corner points P(0, 5), Q(3, 5), R(5, 0), and S(4, 1) with objective function z=ax+2byz = ax + 2by where a,b>0a, b > 0.

When the maximum occurs at two corner points, both points must give the same z-value, and this value must be greater than or equal to the z-values at other corner points.


At P(0, 5):

z=a(0)+2b(5)z = a(0) + 2b(5)

z=10bz = 10b

At Q(3, 5):

z=a(3)+2b(5)z = a(3) + 2b(5)

z=3a+10bz = 3a + 10b

At R(5, 0):

z=a(5)+2b(0)z = a(5) + 2b(0)

z=5az = 5a

At S(4, 1):

z=a(4)+2b(1)z = a(4) + 2b(1)

z=4a+2bz = 4a + 2b


Since maximum occurs at both Q and S, their z-values must be equal:

3a+10b=4a+2b3a + 10b = 4a + 2b

10b−2b=4a−3a10b - 2b = 4a - 3a

8b=a8b = a

a−8b=0a - 8b = 0

Therefore, the condition is a−8b=0a - 8b = 0.

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