Question

The differential equation of all circles in the third quadrant which touch the co-ordinate axes is of order ______.

Options

• 1

• 2

• 3

• 4

Answer 1

The differential equation of all circles in the third quadrant which touch the co-ordinate axes is of order 1.

Explanation:

The equation of the family of circles which touch both the axes is (x + r)² + (y + r)² = r², where r is a parameter.

Since this equation has one arbitrary constant, its order is 1.