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**1. Homework Statement**

Sketch the domain of f(x,y,z) = ln(25-x^2-y^2-z^2) and determine it's range.

**2. Homework Equations**

N/a

**3. The Attempt at a Solution**

Im sure the domain is x^2+y^2+z^2 < 25 or (-infinity, 25)

Then the range is (0,+infinity.)

my problem is how would i sketch it.. i was thinking of a sphere with dotted outline at 5,5,5

2.

**1. Homework Statement**

Specify the type of discontinuity at the origin of the following functions.

2x^y/x^4+y^2

**2. Homework Equations**

N/a

**3. The Attempt at a Solution**

i am not sure how would i find the limit of f(x,y) as (x,y)->(0,0) so i can prove that it is either essential or removable discontinuity..

any help would be great thanks! :D