A table of values for $\displaystyle{f{{\left({x}\right)}}}=-\sqrt{{{x}}}\usepackage{cmbright}\Huge\$ will have no negative values for x because the square root of a negative number is imaginary. There will no positive outputs, because $\displaystyle-\sqrt{{x}}\usepackage{cmbright}\Huge\$ is the negative square root. The shape of the graph of a basic radical function is a half-parabola pointing to the right, so $\displaystyle{f{{\left({x}\right)}}}=-\sqrt{{x}}\usepackage{cmbright}\Huge\$ will be a half-parabola below the x-axis.