Respuesta :
Answer:
see below
Step-by-step explanation:
You want terms that have a common ratio of 3, so the term in the summation will be 3 to some power. Only the first expression matches that requirement.
You can try different values of n to see if they fit the problem description.
n = 1: 1(3)^0 = 1(1) = 1
n = 2: 1(3)^1 = 1(3) = 3
n = 3: 1(3)^2 = 1(9) = 9 . . . . . the third triangle in the set has 9 shaded triangles, as this expression predicts. Thus, we see the problem description being matched by the first answer choice shown.