How do I plot two surfaces on the same axes in Mathematica?

[amcavoy]

If I am using the Plot3D command in Mathematica, how can I plot two separate functions on the same coordinates? Specifically, I am trying to get a picture of the intersection of $x+y+z=1$ with $x^{2}+y^{2}+z^{2}=1$.

 

[heartless]

I suck at mathematica and probably won't help too much, but when I plot many functions or equations I do,
string = Plot[xxxxxxxxxxxxxxxxxxx, DisplayFunction -> Identity]
string2 = Plot[xxxxxxxxxxxxxxxxxxx, DisplayFunction -> Identity]
...
...
...
Show[{string, string2,...}, DisplayFunction -> $DisplayFunction]

It works for both plots2d and 3d in my mathematica. I dunno.

 

[J77]

Plot3D[{1-x-y},{(1-x^2-y^2)^0.5},{x,-10,10},{y,-10,10}]

Should work, I think...

(Although I use Mathematica rarely - Matlab always )

 

[amcavoy]

Those worked, thanks a lot guys .