Finding Differential Equation in RC Circuit with op-amp
By using op-amp rules V+=V-(A=B) I found the following equation....

You are not allowed to apply these rules because the equation (V+=V-) does apply only if the opamp is working linearly.
However, this is not the case, because positive feedback overrules negative feedback. That means: The opamp does not work - it goes immediately into saturation.

In case of a drawing error (both opamp inputs interchanged) we have a damped Deboo integrator (1st order lowpass) with the transfer function 

H(s)=4/(12sC+1)=4/(s+1)

It should not be a problem to transfer this equation into the time domain.