The equation of the directrix of the parabola $y^2+4 y+4 x+2=0$ is

If $\mathrm{f}(x)=\sqrt{1+\cos ^2\left(x^2\right)}$, then $\mathrm{f}^{\prime}\left(\frac{\sqrt{\pi}}{2}\right)$ is

The modulus of the square root of the complex number $6+8 \mathrm{i}$ (where $\mathrm{i}=\sqrt{-1}$ ) is

If $[x]^2-5[x]+6=0$, where [.] denotes the greatest integer function, then