Portfolio type 2 math IB BMI *help*?

Ok so the problem is in graphing and modeling. The portfolio task is modeling in general and thing is that i did most of the tasks but i don't quite know how to get the proof for the task... so im asking people if they have any ideas how to do that they would suggest not give it out but point me into the right direction... thank you so much.

THE DATA :BMI16.40 15.70 15.30 15.20 15.21 15.40 15.80 16.30 16.80 17.50 18.18 18.70 19.36 19.88 20.40 20.85

Age (yrs) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

21.22 21.60 21.65

18 19 20

so and as the graph is ploted in exel i need to make another function that models the data!!!! using technology any suggestions how to do that?

It's kind of urgent !!!!!