# SAT Math Multiple Choice Practice Question 436: Answer and Explanation

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**Question: 436**

**19.** The value of the *n*th term of a sequence is given by the expression *a*^{3n} – 3. If the second term of the sequence is 61, which of the following could be the value of *a* ?

I. –2

II. 2

III. 4

A. I only

B. II only

C. III only

D. I and II only

E. II and III only

**Correct Answer:** D

**Explanation:**

**D** Because 61 is the value of the *second* term in the sequence, plug in 2 for *n*: *a*^{3(2)} – 3 = 61. Therefore, *a*^{6} = 64, and *a* must be equal to ±2. Make sure you read carefully; III would work if 61 were the value of the *first* term.