Write the coefficients of $x^2$ in each of the following: 

(i) $2+x^2+x$ (ii) $2-x^2+x^3$ (iii) $\frac{\mathrm{\pi }}{2}{x}^2+x$ (iv) $\sqrt{2}x-1$

(i) Coefficient of $x^2$ is the numerical value multiplied by $x^2$ in the given polynomial:

$2+x^2+x=2+\left(1\right)x^2+x$

Here, coefficient of $x^2$ is 1.

(ii) Coefficient of $x^2$ is the numerical value multiplied by $x^2$ in the given polynomial:

$2-x^2+x^3=2-\left(1\right)x^2+x^3$

Here, coefficient of $x^2$ is -1.

(iii) Coefficient of $x^2$ is the numerical value multiplied by $x^2$ in the given polynomial:

$\frac{\mathrm{\pi }}{2}{x}^2+x=\left(\frac{\mathrm{\pi }}{2}\right)x^2+x$

Here, coefficient of $x^2$ is $\frac{\mathrm{\pi }}{2}$.

(iv) Coefficient of $x^2$ is the numerical value multiplied by $x^2$ in the given polynomial:

$\sqrt{2}x-1=\left(0\right)x^2+\sqrt{2}x-1$

Here, coefficient of $x^2$ is 0.