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Steverino777
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This is mostly some basic stuff, but I just want to make sure I am doing these right. I have a hard time understanding what the questions are saying sometimes.
1)Explain how we may conclude that if f is a decreasing function, then f(5) < f(3)
Make reference to a logical principle. [Note- By defintion, a function g is decreasing i.f.f the conditional "if x<y, then g(x)>g(y)" is true for any real numbers x and y]
2)Suppose A and B are sets and w is an object, for which it is known that A\subseteqB and w\inA. Explain how we may conclude w\in(A\capB) Make reference to a logical principle.
3)Explain why it is true that if a real number x satisfies |x|>a, but it is not the case that x > a, then x < -a must hold. Make reference to a logical principle.
(p\wedgeq) -> p Law of Simplification
p -> (p\veeq) Law of Addition
[p\wedge(p ->q)] -> q Modus Ponens
[(p\veeq)\wedge ~q] -> p Modus Tollendo Ponens
[(p -> q)\wedge~q] -> ~p Modus Tollens
(p -> r) -> [(p\wedgeq) -> r]
[~p -> (q\wedge~q] -> ~p Law of Contradiction
1) The definition of a decreasing function states, "if x<y, then g(x)>g(y)" is true for any real numbers x and y. By hypothsis we know f is a decreasing function, so that the preticular case of the definition, "if 5 < 3, then g(5) > g(3)" is known to be true. --That's as far as I can get using an example form the book as a guideline. I'm not sure where to go from here and which logical principle applies to this argument.--
2) --I know how to explain it but I don't know which logical principle to use.--
A\subseteq B includes all the elements in A that are also elements of B. Since it is given w\in A, by this definiton w is also an element of B. A\capB includes only the elements that A and B share in common. Since w is both an element of A and B, it is one of the elements that A and B share in common, making it an element of A\capB.
3)If a real number x satisfies |x|>a, that means x < -a or x > a. It is also given that it is not the case that x > a. Therefore by Modus Tollendo Ponens we can conclude that x < -a.
If anyone could help me with finding which logical principles apply to one and two, that'd help a lot.
Homework Statement
1)Explain how we may conclude that if f is a decreasing function, then f(5) < f(3)
Make reference to a logical principle. [Note- By defintion, a function g is decreasing i.f.f the conditional "if x<y, then g(x)>g(y)" is true for any real numbers x and y]
2)Suppose A and B are sets and w is an object, for which it is known that A\subseteqB and w\inA. Explain how we may conclude w\in(A\capB) Make reference to a logical principle.
3)Explain why it is true that if a real number x satisfies |x|>a, but it is not the case that x > a, then x < -a must hold. Make reference to a logical principle.
Homework Equations
(p\wedgeq) -> p Law of Simplification
p -> (p\veeq) Law of Addition
[p\wedge(p ->q)] -> q Modus Ponens
[(p\veeq)\wedge ~q] -> p Modus Tollendo Ponens
[(p -> q)\wedge~q] -> ~p Modus Tollens
(p -> r) -> [(p\wedgeq) -> r]
[~p -> (q\wedge~q] -> ~p Law of Contradiction
The Attempt at a Solution
1) The definition of a decreasing function states, "if x<y, then g(x)>g(y)" is true for any real numbers x and y. By hypothsis we know f is a decreasing function, so that the preticular case of the definition, "if 5 < 3, then g(5) > g(3)" is known to be true. --That's as far as I can get using an example form the book as a guideline. I'm not sure where to go from here and which logical principle applies to this argument.--
2) --I know how to explain it but I don't know which logical principle to use.--
A\subseteq B includes all the elements in A that are also elements of B. Since it is given w\in A, by this definiton w is also an element of B. A\capB includes only the elements that A and B share in common. Since w is both an element of A and B, it is one of the elements that A and B share in common, making it an element of A\capB.
3)If a real number x satisfies |x|>a, that means x < -a or x > a. It is also given that it is not the case that x > a. Therefore by Modus Tollendo Ponens we can conclude that x < -a.
If anyone could help me with finding which logical principles apply to one and two, that'd help a lot.
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