A line passes through (2,1), (0,-2), (-2,-3), what is the y intercept?
It will be
You can see this from your second set of coordinates where for
Obviously, given the second data point
but the given data points (2,1), (0,-2), (-2,-3) are not points on a straight line,
The underlying equation could be a parabola (with a horizon axis of symmetry) or some more complex relationship.
Other y-intercepts are possible.