Question 880141
Not a complete answer yet - but the points appear to be logarithmic.


The points shown in the hyperlink are (2,12),(4,23),(6,33),(8,40),(10,45), in which first coordinate is months age and the second coordinate is weight.


Starting with {{{y=a*ln(x)+b}}}, forming two equations from the first and last ordered pair, and solving the system, a model found is {{{highlight(y=(20.5)ln(x)-2.21)}}}.  This model is good but does not reproduce the point (4,23) nor (6,33) too well.


Trying a quadratic model, using the points (2,12), (6,33), and (10,45) gave three simultaneous equations.  The resulting coefficients while treating the actual a, b, and c of general form as the variables, fed into the perdue matrix calulator ( http://www.math.purdue.edu/~dvb/matrix.html ), gives {{{highlight_green(y=-0.2813x^2+7.5x-1.875)}}}.   You can check how well this model fits and decide what you think of it.


That quadratic model appears to reproduce the data points very well...