$\"\"$ \ \

The function is $\"\"$ . \ \

Find $\"\"$ . \ \

First find the first partial derivative $\"\"$ . \ \

$\"\"$ . \ \

Differentiate partially with respect to $\"\"$ treating $\"\"$ and $\"\"$ as constant. \ \

$\"\"$ \ \

Substitute $\"\"$ , $\"\"$ and $\"\"$ . \ \

$\"\"$ \ \

$\"\"$ . \ \

$\"\"$ \ \

$\"\"$ .