By inspecting the Karnaigh map plot of the switching function

By inspecting the Karnaigh map plot of the switching function F (X₁, X₂, X₃) = Σm (1, 3, 6, 7), one can say that the redundant prime implicant is—

Given, F (X₁, X₂, X₃) = ∑ m (1, 3, 6, 7)
From K-map. The redundant prime implicant is X₂, X₃.