Q.Lagrange's interpolation formula can be used for :

Lagrange's interpolation formula is defined for arbitrary distinct arguments $x_0,x_1,\dots,x_n$, so it applies to both equal and unequal intervals; option (b).

Why. Lagrange's formula,

$y=\sum_{i=0}^{n} y_i\,\prod_{j e i}\frac{x-x_j}{x_i-x_j},$

uses the actual differences $(x_i-x_j)$ of the given nodes. It never requires the spacing to be constant.

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