4. Consider again the structure R = (IR, +, x, <) and let P(x, y) be the predicate a < y. Express the predicate using a formula p(x, y) involving only + and x and not involving <. That is, find a formula p(x, y) such that P(x, y) and p(x, y) are logically equivalent in R with p(x, y) not involving the symbol <.

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
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3. Consider the structure R =
(IR, +, ×, <). We say that a set C CR is definable in R if
there is a formula p(x) such that c E C if and only if p[c] is true in R. Show that the set
C = {0,1} is definable in R.
(Hint: Consider the polynomial whose solution is exactly 0 or 1.)
4. Consider again the structure R
(IR, +, ×, <) and let P(x, y) be the predicate x < y.
Express the predicate using a formula p(x, y) involving only + and × and not involving <.
That is, find a formula p(x, y) such that P(x, y) and p(x, y) are logically equivalent in R
with p(x, y) not involving the symbol <.
Transcribed Image Text:3. Consider the structure R = (IR, +, ×, <). We say that a set C CR is definable in R if there is a formula p(x) such that c E C if and only if p[c] is true in R. Show that the set C = {0,1} is definable in R. (Hint: Consider the polynomial whose solution is exactly 0 or 1.) 4. Consider again the structure R (IR, +, ×, <) and let P(x, y) be the predicate x < y. Express the predicate using a formula p(x, y) involving only + and × and not involving <. That is, find a formula p(x, y) such that P(x, y) and p(x, y) are logically equivalent in R with p(x, y) not involving the symbol <.
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