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Jawab

x+ 3y = 9
y =0 , x= 9 –> (9,0)

x + y = 5
x = 0 , y = 5 –> (0,5)

x+ 3y = 9
x + y = 5 …..(-)
2y = 4
y = 2 
x = 3 …..(3, 2)

f(x,y )  = 5x + 7y
f(9,0) = 45
f(0,5) = 35
f(3,2) = 15 + 14= 29
Minimum = 29