What do $C$ and $Si$ possess among the following?

The position vectors of two particles of masses $1 \, kg$ and $3 \, kg$ are $\hat{i} + 2\hat{j} + \hat{k}$ and $-3\hat{i} - 2\hat{j} + \hat{k}$ respectively. The position vector of the center of mass of the system of these particles is:

Raoult's law is obeyed by each constituent of a binary liquid solution when

Let $\overrightarrow{a}=\hat{i}-2 \hat{j}+3 \hat{k}$,$\overrightarrow{b}=2 \hat{i}+3 \hat{j}-\hat{k}$ and $\overrightarrow{c}=\lambda \hat{i}+\hat{j}+(2 \lambda-1) \hat{k}$. If $\overrightarrow{c}$ is parallel to the plane containing $\overrightarrow{a}$ and $\overrightarrow{b}$,then $\lambda$ is equal to

The inverse point of $(1,2)$ with respect to the circle $x^2+y^2-4x-6y+9=0$ is

The solution of the differential equation $(3xy + y^2)dx + (x^2 + xy)dy = 0$ is