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) ).
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.
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) ).