That requires a bit of name-value pair arguments to the fcontour function.
Try this:
syms f(x,y) x y
f(x,y) = x^2 + (3*y/2 - sqrt(abs(x)))^2;
figure
fcontour(f, [-2 2], 'MeshDensity',250, 'LevelList',[3 3])
grid on
The 'LevelList' name-value pair argument is important here, since it will draw the contour where your function equals 3. .
I hope this is not homework. However, it likely requires a bit more familiarity with the MATLAB plot functions than someone just now learning MATLAB is likely to have.
