1. (25) Given a CFG G-(V, S, P), a variable X of G is said to be useful if X appears in a derivation S-* αχβ-‘ w E Σ*. Prove formally that Li E P, where L,-{(G, X〉 1 X is useful in CFG G} Show transcribed image text 1. (25) Given a CFG G-(V, S, P), a variable X of G is said to be useful
OR
OR