Answer
$a.\quad 7$
$b.\quad 0$
$c.\quad\sqrt{35}$
$d.\quad\sqrt{\dfrac{21}{2}}$
Work Step by Step
$ a.\quad$
$f(0, 0,0)=\sqrt{49-0-0-0}=7$
$ b.\quad$
$f(2, -3,6)=\sqrt{49-4-9-36}=0$
$ c.\quad$
$f(-1,2,3)=\sqrt{49-1-4-9}=\sqrt{35}$
$ d.\quad$
$f(\displaystyle \frac{4}{\sqrt{2}}, \frac{5}{\sqrt{2}}, \frac{6}{\sqrt{2}})=\sqrt{49-\frac{16}{2}-\frac{25}{2}-\frac{36}{2}}=\sqrt{\frac{98-77}{2}}=\sqrt{\frac{21}{2}}$
