Answer
Refer to the sketch in the picture
Work Step by Step
$f(x,y)=\sqrt (x2+y2)$
In order to draw the graph we need to know the number of independent variables (n), which will help us figure out the number dimensions needed to draw the graph.
The function has two independent variables x,y
The dimension (m) = n+1
Hence we need three dimensions, that is, x,y,z
But the third dimension is the value of the function, that is, $z=\sqrt (x^2+y^2)$
We need a set of values of x,y which will help us find z
[NB: There should be no negative values under the square root, hence the values of x and y selected must not give a negative number under the square root]
Finding the range of values we need in plotting our graph
$x2+y2≥0$ But $x, y$ are squared so any value of $x, y$ will produce a positve value for $z$
This information helps us to graph our function in three dimensions (x,y,z)