How to use this class

I don't know how to use this class.
I have this code:

$class1 = new IntersectionPointsOf2Circles(2, 3, 3, 1, -1, 4);
$points = $class1->getPoints();

and I don't know how to show each intersection point.
When i try this:

echo $points[0]['x'];

I get error: Undefined offset: 0

I've tried everything and I'll passed:(
Can anybody help me?