The A*B+C is a dual, four-quadrant multiplier with VC Offset.
Each section can perform the analog multiplication of two signals (A and B) and add an offset (C). It can also act as a dual voltage controlled attenuverter, dual ring modulator, dual VCA or four channel mixer (see block diagram below).
The B inputs are routed to an attenuverter that multiplies the signal between -2 to 2, while the offset inputs (C) route through a unity gain attenuverter (multiplies the signal between -1 and 1).
B and C inputs are normalised to 5v and 10v respectively, so the A inputs can be processed using just the potentiometers.
The output of first block is normalized to the second one, so the second output can act as master to get (A1*B1+C1) + (A2*B2+C2).