Need help with discrete math problem

[chillerbros17]

4. Let the domain d be the set of nonzero real numbers. D is the domain for both x and y. For each part, decide whether the statement is true or false. If statement is true, explain why. If statement is false, find negation and explain why negation is true.

a. (There exists x) (for all y) xy= 1
b. (For all x) (There exists y) xy=1
c. (For all x) (for all y) [ sin^2x + cos^2x = sin^2y + cos^2y ]
d. (There exists x) (There exists y) [ 2x+y = 5 ^ x-3y = -8 ]

 

[pka]

Again what have you done on any of these?
Can you tell what you don't understand about these?
These are your problems, please show some effort.