Which method is used to obtain virus-free plants?

When a capacitor is connected in series to an $LR$ circuit,the alternating current flowing in the circuit

The image of the point $(3, 8)$ in the line $x + 3y = 7$ is

Consider a system of three charges $\frac{q}{3}, \frac{q}{3}$ and $-\frac{2q}{3}$ placed at points $A, B$ and $C$ respectively,as shown in the figure. Take $O$ to be the centre of the circle of radius $R$ and $\angle CAB = 60^\circ$.

$A$ rod is fixed between two points at $20^{\circ}C$. The coefficient of linear expansion of the material of the rod is $1.1 \times 10^{-5} /^{\circ}C$ and Young's modulus is $1.2 \times 10^{11} \, N/m^2$. Find the stress developed in the rod if the temperature of the rod becomes $10^{\circ}C$.

If the harmonic mean of the roots of the equation $\sqrt{2}x^2 - bx + (8 - 2\sqrt{5}) = 0$ is $4$,then the value of $b$ is: