About Fit a Two-Term Exponential Model

Hi,

1. What does 'StartPoint' mean in this code: f = fit(x,y,'exp1','StartPoint',[1,2]) plot(f,x,y)

2. The blue and black curves are origin data. The red and magenta curves are the fitted curves ('exp2').

I want the end point of the red curve is the same with the start point of the magenta curve. Is it possible? If it is possible, Which command can be used for this case?

If I want the derivation at the junction between red and magenta curves are the same. Is it possible? If it is possible, Which command can be used for this case?