∃x p(x)∧∃x q(x) and ∃x (p(x)∧q(x))
suppose domain consist of all positive integers
p(x)= x is odd q(x)= x is even
consider ∃x p(x)∧∃x q(x) ,it is saying that there exist odd numbers and there exist even numbers
now consider ∃x (p(x)∧q(x)) it is saying that there exist a no. which is is both odd and even it is trivially false.