Which salt is used as a purgative?

$A$ wire elongates by $l \, mm$ when a load $W$ is hanged from it. If the wire goes over a pulley and two weights $W$ each are hung at the two ends,the elongation of the wire will be (in $mm$):

In Young's double slit experiment,the seventh maximum with wavelength ${\lambda _1}$ is at a distance $d_1$ from the central maxima,and the same maximum with wavelength ${\lambda _2}$ is at a distance $d_2$. Then the ratio $d_1/d_2$ is:

$ \int \frac{\sin 2x}{\sin^2 x + 2\cos^2 x} dx = $

Which one is an incorrect statement?

$\left\{x \in R: \frac{2x-1}{x^3+4x^2+3x} \in R\right\}$ equals