If the percentage error in the radius of circle is 3 , then the percentage error in its area is

The equation of the tangent to the curve $y=x^3-2 x+7$ at the point $(1,6)$ is

The distance ( s ) travelled by a particle in time $t$ is given by $S=4 t^2+2 t+3$. The velocity of the particle, when $t=3 \mathrm{sec}$ is

If $a^2 x^4+b^2 y^4=c^6$, then maximum value of $x y$ is equal to