Benzaldehyde reacts with ammonia to form

$\int \frac{3^x dx}{\sqrt{9^x-1}}$ is equal to

Eight spherical rain drops of the same mass and radius are falling down with a terminal speed of $6 \ cm \ s^{-1}$. If they coalesce to form one big drop,what will be the terminal speed of the bigger drop? (Neglect the buoyancy of the air) ....... $cm \ s^{-1}$

Which of the following taxonomic categories is being described by the given statements $(i-iii)$?
$(i)$ It is the basic unit of classification.
$(ii)$ It is defined as the group of individuals which resemble in their morphological and reproductive characters and interbreed among themselves and produce fertile offsprings.
$(iii)$ Human beings belong to the species sapiens which is grouped in the genus Homo.

$A$ minimum value of $\int_0^x t e^{t^2} d t$ is

$\frac{(1+i)^{2011}}{(1-i)^{2009}}$ is equal to