Answer
$y=2$
Work Step by Step
The radius of circle is $2$
If the circle is rolled along the $x-$axis, it looks as below.
From the below figure, when $x$ coordinate of centre of circle is changed, the $y$ coordinate remains constant and it is equal to the radius of circle $2$
Therefore, the equation of path of the center of the circle of radius $2$, if it is made to roll along $x$-axis is $y=2$.
