Given any finite number of data points there exist an
infinite number of functions that give those data points. It is true that given n data points there exist a unique
polynomial of degree n- 1 that gives those data points. You can find that polynomial using the 'Lagrange interpolating formula':
P(x)=i=1∑nyn(xi−x1)(xi−x2)⋅⋅⋅(xi−xi−1)(xi−xi+1⋅⋅⋅(xi−xn)x−x1)(x−x2)⋅⋅⋅(x−xi−1)(x−si+1⋅⋅⋅(x−xn).
Here, with this data 6 data points, (-11, 1), (-10, 2), (-7, 5), (-3, 9), (2, 14), and (6, 18). The Lagrange interpolating polynomial is the fifth degree polynomial
1(−11+10)(−11+7)(−11+3)(−11−2)(−11−6)(x+10)(x+7)(x+3)(x−2)(x−6)+2(−10+11)(−10+7)(−10+3)(−10−2)(−10−6)x+11)(x+7)(x+3)(x−2)(x−6)+5(−7+11)(−7+10)(−7+3)(−7−2)(−7−6)x+11)(x+10)(x+3)(x−2)(x−6)+9(−3+11)(−3+10)(−3+7)(−3−2)(−3−6)x+11)(x+10)(x+7)(x−2)(x−6)+14(2+11)(2+10)(2+7)(2+3)(2−6)x+11)(x+10)(x+7)(x−2)(x−6)+18(6+11)(6+10)(6+7)(6+3)(6−2)(x+11)(x+10)(x+7)(x+3)(x−2). Of course that might not be the simplest function interpolating these points. As I said there are an infinite number of functions that will give these points.