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  1. GATE CS
  2. PYQs
  3. Discrete Mathematics

Symbolize the expression "Every mother loves her children" in predicate logic.

GATE 1989 · Discrete Mathematics · First Order Logic · medium

Answer: forall x [ M(x) -> forall y ( C(y, x) -> L(x, y) ) ], equivalently forall x forall y ( (M(x) AND C(y, x)) -> L(x, y) ).

  1. Quantify over all mothers: The phrase 'every mother' becomes forall x ( M(x) -> ... ), so non-mothers make the implication vacuously true and only mothers are constrained.
  2. Quantify over her children and state the loving: Inside the body, 'loves her children' means: for every y that is a child of x, x loves y, i.e. forall y ( C(y,x) -> L(x,y) ).