The coefficient of $x^4$ in the expansion of $\frac{(1-3x)^2}{(1-2x)}$ is equal to

In the compound $M-O-H$,the $M-O$ bond will be broken if

Which of the following is not a synthetic polymer?

Which of the following oxides produces $H_2O_2$ when treated with $HCl$?

Which of the following statements are correct?
$I$. $P_4$ molecule is very reactive because of angular strain.
$II$. The basicity of $H_3PO_3$ is $3$.
$III$. In gas phase,all $P-Cl$ bonds of $PCl_5$ have same bond length.
$IV$. In solid state,$PCl_5$ exists as an ionic solid,in which anion $[PCl_6]^-$ has octahedral and cation $[PCl_4]^+$ has tetrahedral shape.

The value of $k$ for which the equation $x^2-4xy-y^2+6x+2y+k=0$ represents a pair of straight lines is equal to ........