If $f(x) = \frac{x^2}{x+a}$,then $f^{\prime \prime}(a)$ is equal to

Let $f(x) = \frac{\sin x + \cos x - \sqrt{2}}{\sin x - \cos x}$,$x \in [0, \pi] - \{\frac{\pi}{4}\}$. Then $f(\frac{7\pi}{12}) f''(\frac{7\pi}{12})$ is equal to

Find the second order derivative of the function $f(x) = x^{2} + 3x + 2$.

If $y=\frac{\log _e x}{x}$ and $z=\log _e x$, then $\frac{d^2 y}{d z^2}+\frac{d y}{d z}$ is equal to

If $y = \frac{1}{x} + \cos 2x$, then $\frac{d^2y}{dx^2}$ is equal to

If $a \neq b, x \neq n \pi, n \in Z$ and $y^2 = a^2 \cos^2 x + b^2 \sin^2 x$,then $\frac{d^2 y}{dx^2} + y =$