First, you need to define your terms. I'm guessing that "B" is one of the coefficients of the quadratic approximation of the thermistor resistance as a function of temperature.
Second, don't assume anything not in the datasheet. Don't guess, check.
The temperature to resistance function of thermistors can be quite complex and is dependent on the material used. There are various thermistor materials out there, and there can be differences in the exact formulation within the same basic types.
The quadratic approximation is just that, a approximation. Usually second order is good enough so that the remaining error is below the thermistor's inaccuracy anyway, but don't assume everyone uses this approximation. This usually works well enough for the high accuracy types, like platinum, but the much cheaper lower temperature thermistors used to sense power supply overheating and the like have a different function and are much less accurate. Often a exponential or a software lookup table is used. Again, you can't assume.