Inference Rule with Quantifier and implication

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master cherundo
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Homework Statement


All healthy food does not taste good. "
Spinach is a healthy food. Duncan only want to eat tasty food. Duncan does not eat spinach. Hamburger is not a healthy food.

Write all possible conclusion.
I try to translate it into proposition with quantifier, such as [tex]t(x)=[/tex]x is tasty, [tex]h(x)=[/tex]x is healthy, [tex]d(x)=[/tex] Doddy eats x.

The Attempt at a Solution



I think [tex]d(hamburger)[/tex] is not a conclusion because the argument is [tex]d(x) \rightarrow t(x)[/tex]. We cannot conclude [tex]d(hamburger)[/tex] or [tex]t(hamburger)[/tex], because proposition said [tex]h(x) \rightarrow ~t(x)[/tex] and [tex]d(x) \rightarrow t(x)[/tex]. Is it right?
 
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Yes, that is correct. (Assuming that "Doddy" is a nickname for "Duncan"!) Saying "All healthy food does not taste good" does NOT imply that unhealthy food does taste good. Of course, "not d(spinach)" would be a conclusion from the first two statements but that is given as the third statement.