Which branch of science is associated with the development and cultivation of forests?

If the slope of one line of $ax^2 + 4xy + y^2 = 0$ is $3$ times the other,then the value of $a$ is:

The eccentricity of the ellipse $x^2+4y^2+2x+16y+13=0$ is

If $\sqrt{\frac{y}{x}}+\sqrt{\frac{x}{y}}=2$,then $\frac{d y}{d x}$ is equal to

The calculated magnetic moment (in Bohr magnetons) of $Cu^{2+}$ ion is

The work function of a metallic surface is $5.01 \ eV$. The photo-electrons are emitted when light of wavelength $2000 \ \mathring{A}$ falls on it. The potential difference applied to stop the fastest photo-electrons is ............. $volts$ $[h = 4.14 \times 10^{-15} \ eV \ s]$