Question

The order of the differential equation of the family of all concentric circles centred at $\left(h,k\right)$ is

• A. $1$
• B. $2$
• C. $3$
• D. $4$

Answer 1

The correct option is A

$1$

Explanation for the correct option

Equation of the circle : ${\left(x-h\right)}^{\mathbf{2}}\mathbf{+}{\left(y-k\right)}^{\mathbf{2}}\mathbf{=}{\mathit{r}}^{\mathbf{2}}$ where $r$ is the radius of the circle

Here $\left(h,k\right)$ are given constants and only radius $r$ is the variable.

Therefore given equation contain only $1$ variable

So the order of the differential equation is $1$

Hence, the correct option is $\left(\mathrm{A}\right)$.