The eccentricity of the ellipse $9x^2 + 5y^2 - 30y = 0$ is

Which of the following statements is not valid for oxoacids of phosphorus?

If $\log _{27}(\log _3 x) = \frac{1}{3}$, then the value of $x$ is

If $f: \mathbb{R} \rightarrow \mathbb{R}$ is such that $f(x+y) = f(x) + f(y)$ for all $x, y \in \mathbb{R}$,$f(1) = 7$,and $\sum_{r=1}^n f(r) = 14112$,then $n = $

In the case of a simple pendulum executing $SHM$,at $t=0$,the bob is not at the mean position. The graph drawn between the tension $(T)$ in the string and time $(t)$ is

When a spring is stretched by $2 \ cm$,it stores $100 \ J$ of energy. If it is further stretched by $2 \ cm$,the stored energy will be increased by $.... \ J$.