Question

Q. Find the minimum value of Q=x^2y subject to the constraint 2x^2+4xy=294.


Its the derivative method.

Answer 1

Hints:
Here you have two variables, and one constraint. From the constraint, y can be solved in terms of x. This value of y can then be substituted into Q to make Q a function of Q=Q(x), whose minimum value can be calculated by differentiation.
I get x=±7√2.
Check each to make sure it is a minimum or maximum.