To figure this out we know that each number in the ordered pair must be multiplied or by divided by the same number. We will see if each number has the same multiplier or divisor below.
8/4=2 -4/4=-1 (2,-1) is a dilation.
8/4=2 -4/4=-1≠-2
(2,-2) is not a dilation. The two numbers do not have the same divisor to get to the final figure. I hope this helps!