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given data points (1,2), (2,4), and (3,6).

using lagrange interpolation, I get the polynomial as f(x) = 2x. Now can I use this polynomial to find f (18) [note that 18 lies outside the range of x's of given data points (ie 1 to 3)]?

I will get f(18) = 36. But is this conceptually correct?

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