20 is divided into two parts so that the product of the cube of one part and the square of the other part is maximum, then these two parts are

The acute angle between the diagonals of a parallelogram whose vertices are $\mathrm{A}(2,-1)$, $B(0,2), C(2,3)$ and $D(4,0)$ is

The shortest distance between the line $y-x=1$ and the curve $x=y^2$ is

The equation of the circle passing through the point $(1,1)$ and having two diameters along the pair of lines $x^2-y^2-2 x+4 y-3=0$ is