What will be the negation of this statement:

Yes, that works.

In logic, the original is:

$\forall x (S(x) \rightarrow \exists y (H(y) \land I(y,x) \land \exists z (P(z) \land L(z,y) \land ((R(x) \land B(x)) \lor (E(x) \land K(x)))))$

If you negate this:

$\neg \forall x (S(x) \rightarrow \exists y (H(y) \land I(y,x) \land \exists z (P(z) \land L(z,y) \land ((R(x) \land B(x)) \lor (E(x) \land K(x))))) \Leftrightarrow$

$\exists x \neg (S(x) \rightarrow \exists y (H(y) \land I(y,x) \land \exists z (P(z) \land L(z,y) \land ((R(x) \land B(x)) \lor (E(x) \land K(x))))) \Leftrightarrow$

$\exists x (S(x) \land \neg \exists y (H(y) \land I(y,x) \land \exists z (P(z) \land L(z,y) \land ((R(x) \land B(x)) \lor (E(x) \land K(x))))) \Leftrightarrow$

$\exists x (S(x) \land \forall y \neg(H(y) \land I(y,x) \land \exists z (P(z) \land L(z,y) \land ((R(x) \land B(x)) \lor (E(x) \land K(x))))) \Leftrightarrow$

$\exists x (S(x) \land \forall y (H(y) \land I(y,x) \rightarrow \neg \exists z (P(z) \land L(z,y) \land ((R(x) \land B(x)) \lor (E(x) \land K(x)))))$

.. which is what your sentence says

If we push the negation further in, we get:

$\exists x (S(x) \land \forall y (H(y) \land I(y,x) \rightarrow \forall z \neg (P(z) \land L(z,y) \land ((R(x) \land B(x)) \lor (E(x) \land K(x)))))\Leftrightarrow$

$\exists x (S(x) \land \forall y (H(y) \land I(y,x) \rightarrow \forall z (P(z) \land L(z,y) \rightarrow \neg ((R(x) \land B(x)) \lor (E(x) \land K(x)))))\Leftrightarrow$

$\exists x (S(x) \land \forall y (H(y) \land I(y,x) \rightarrow \forall z (P(z) \land L(z,y) \rightarrow (\neg (R(x) \land B(x) \land \neg (E(x) \land K(x))))\Leftrightarrow$

$\exists x (S(x) \land \forall y (H(y) \land I(y,x) \rightarrow \forall z (P(z) \land L(z,y) \rightarrow ((\neg R(x) \lor \neg B(x) \land (\neg E(x) \lor \neg K(x))))$

which translates to:

"There is a street in the city where for every house in that street it is true that every person living in that house is not rich or not beautiful, and is also not highly educated or not kind"


Your answer is correct as far as it goes. Your instructor might want you to continue by changing

we can find no person ...

to

every person ...

and changing the ands and ors in the ... appropriately.


The negation is NOT(Every street in the city has at least one house in which we can I find a person who is rich and beautiful or highly educated and kind.)

Which means --- NOT Every street in the city has at least one house in which we can I find a person who is rich and beautiful or highly educated and kind.

Which is equivalent to your statement.