Function that shouldn't be able to generate complex numbers giving me complex results

Basically the original question. I've got a function that shouldnt physically be able to give me complex numbers (the only thing that is taken to a root is a sum of two squares, which has to be positive). I've included the code that I have here. If someone could give me some info on why this is returning complex outputs I would love you forever.

f = @(x1,x2)((1/5)*((x1)^2 + (x2)^2)^(3/2) - (x1^2 + x2^2) + x1/2 + x2/2 + 7);
lim=[-5,0,-5,0];

X1 = linspace(lim(1),lim(2),10);
X2 = linspace(lim(3),lim(4),10);
[x1,x2] = meshgrid(X1,X2);

f(x1,x2)

The only reason I really care is that i'm trying to take this function and put it into the surf function, which threw the error

Error using surf (line 71)

X, Y, Z, and C cannot be complex.

I did a little hunting on my own, and discovered that for some reason, when I put just straight values (like if I were to call f(-4, -3)) it returns a positive decimal number, but when I pass the two matrices, it returns a bunch of complex numbers.

Answer 1

[Ryan Berry]

Never mind I figured it out.

For anyone else who may run into this issue - because I was inputting a pair of matrices, raising stuff to powers becomes weird. I wanted to raise each individual number to the 3/2, and so I had to do

((x1.^2) + (x2.^2)).^(3/2)

Without the dot modifier on the to the 3/2, it returns complex numbers.