Hello, lingyai!

Your work is correct!

The looks like they differentiated with respect to x . . . but even that is wrong.If , find

a) the partial derivative of with respect to

b) the partial of with respect to

The method I am using is to treat all x's as constants and to take the derivative of all y's.

For a) I get:

. . . . . which matches the book's answer.

For b) I use the same approach.

If , then should be:

. .. . . Correct!

The book, however, gives the answer as:??

Am I missing something? . . . Not a thing!

If , then:

Since , then

Their answer doesn't matchanythingin the problem!

. . It must be just one more typo on their part.