The first derivative of a function f ∈ C^∞(−3, 3) is approximated by an interpolating polynomial of degree 2, using the data 

(−1, f(−1)), (0, f(0)) and (2, f(2)). 

It is found that

f′(0) ≈ −\(\frac{2}{3}\) f(−1) + αf(0) + βf(2).

Then, the value of \(\frac{1}{\alpha \beta}\) is