The sum of the perimeter of a circle and square is k, where k is some constant. Prove that the sum of their areas is least when the side of square is double the radius of the circle.

Explanation

`text(Let x be the radius of the circle and y be the side of the square)`



`text(Given: Sum of the perimeter of the circle and the square is k.)`



`therefore 2pi(radius)+4(side)=k`


...