Question

Find the maximum value of xy :
if x + 3y = 12
(c) 12​

Answer 1

Step-by-step explanation:

x = 12 when y = 0

y = 4 when x = 0

1. 12+3×0

12+0

12

2. 0+3×4

0+12

12

Answer 2

x + 3y = 12

x = 12 - 3y

Now let f = xy

So, f=(12 - 3y)*y

f = 12y - 3y^2

Now df/dy = 12 - 6y

For f=xy to be maximum

df/dy = 12 - 6y = 0

y = 2

So x = 6

So maximum value of xy is 12