1. A computing device comprising: a microprocessor for executing general purpose programs, wherein the microprocessor has at least one output port for transmitting data and at least one input port for receiving data; and a neural network co-processor, operatively coupled to the at least one input port and the at least one output port, for computing at least one mathematical function that includes a polynomial expansion having a form ##EQU4## wherein y represents an output of said neural network co-processor w.sub.i-1 represents a weight value, x.sub.1, x.sub.2,.. . , x.sub.n represent inputs to said neural network co-processor, g.sub.1i,. .. , g.sub.ni represent gating functions and m and n are integers.