Pfthb

The two-argument function check returns True exactly when both
Boolean operands have the same value. Otherwise it returns False.
I should implement it using :

check :: Bool -> Bool -> Bool

1)- Conditional expressions(checkA)

checkA x y = if x < y then False else True

-
2)-Guarded equations (checkB).

checkB x y | x < y = False | otherwise =True

3)-Pattern matching (checkc).

,but here I get an error

checkC x y False False = True
 True True = True
 False True = False
 True False = False

How can I use Pattern matching to say (if this and that are equivalent then ...) when x and y are numbers(int)?

You can pattern match against bools because there's a finite (and small) number of combinations. Consider the whole combination space of Bools (which is defined as n^n where n is the size of the space)

False False
False True
True False
True True

It's trivial to enumerate these by hand in check

check :: Bool -> Bool -> Bool
check False False = True
check False True = False
check True False = False
check True True = True

But as you can deduce, Ints are not as trivial, since the space of all integers is literally infinite.

You can pattern match in this way with ints if you have an infinite amount of programming time and hard drive space, because you have an infinite amount of patterns to write.

check :: Int -> Int -> Bool
check 0 0 = True
check 1 1 = True
check (-1) (-1) = True
check 2 2 = True
check (-2) (-2) = True
-- etc literally until infinity
check _ _ = False

The way to write this is to either use guards:

check :: Int -> Int -> Bool
check x y | x == y = True
 | otherwise = False

Or realize that there is a pretty standard function that already does this -- maybe you've heard of it? :-)

check :: Int -> Int -> Bool
check = (==)