Point (a, b) is transformed by the rule (a, b−4) .

what type of transformation occurred?

a translation of 4 units to the right

a translation of 4 units to the left

a translation of 4 units up

a translation of 4 units down

Any change made in the first coordinate, is a change of the point in the horizontal direction.

Similarly, any change made in the second coordinate, is a change of the point in the vertical direction.

Thus the rule (a, b)→(a, b-4) is a rule which affects the point only in the vertical position.

The point (a, b) is shifted 4 units down (because of -4)

 a translation of 4 units down