## Thomas' Calculus 13th Edition

$7, 0, \sqrt {35} , \sqrt \frac{21}{2}$
$f(x,y,z) = \sqrt {49-x^2 - y^2 - z^2}$ a) $f(0,0,0) = \sqrt {49} = 7$ b) $f(2,-3,6) = \sqrt {49-4-9-36} = 0$ c) $f(-1,2,3) = \sqrt {49-1-4-9} = \sqrt {35}$ d) $f(\frac{4}{\sqrt 2}, \frac{5}{\sqrt 2}, \frac{6}{\sqrt 2}) = \sqrt {\frac{21}{2}}$