The first formula should be , and similarly for the second.
The use of implication is correct. These statements are true for all x, including those for whom the premises are false.
To run a marathon you must be over 5 feet and have a healthy heart. If you are not over 5 feet and do not have a healthy heart, you cannot run the marathon. Right this statement in symbols.
Let a(x) be the assertion "x can run the marathon"
For the first statement I got
For the second statement I got
I have a feeling this is wrong because if the hypothesis is false then the statment is true, if I don't use implication what do I use?