1. Find the optimal values ​​of the function. f (x, y) = 4xy + 5 Subject to the restriction x ^ 2 + y ^ 2 = 18 2. Find by the method of Lagrange multipliers, the critical points of the functions...

1. Find the optimal values ​​of the function.
f (x, y) = 4xy + 5
Subject to the restriction x ^ 2 + y ^ 2 = 18
2. Find by the method of Lagrange multipliers, the critical points of the
functions subject to the indicated restrictions:
a) f (x, y) = x ^ 2 + 4y ^ 2 + 6; 2x-8y = 20
b) f (x, y) = 2x ^ 2 + 5y ^ 2 + 7; 3x-2y = 7