I was using This Wolfram Alpha Page to calculate the partial derivatives of the sum of two gaussians. It believes the answer to be: $ e^{-(b-x)^2/2 c^2} $ but the working shows it as ending on: $ e^{-(x-b)^2/2 c^2} $ Which is what I had thought the answer was.
Is this a bug in Wolfram's engine or have I missed an obvious step?