The sum of two nonzero numbers is 4 . The minimum value of the sum of their reciprocals is

The combined equation of the tangent and normal to the curve $x y=15$ at the point $(5,3)$ is________

The angle between the line $x=\frac{y-1}{2}=\frac{z-3}{\lambda}$ and the plane $x+2 y+3 z=6$ is $\cos ^{-1} \sqrt{\frac{5}{14}}$, then the value of $\lambda$ is

The length and breadth of a rectangle are $x_{x \mathrm{~cm}}$ and $y \mathrm{~cm}$ respectively. If the length decreases at the rate of $5 \mathrm{~cm} /$ minute and the breadth increases at the rate of $3 \mathrm{~cm} /$ minute, then the rates of change of the perimeter and area respectively when the length is 5 cm and breadth is 2 cm , are