Given the first five terms of the sequence 19, 15, 11, 7, 3 . . . . , use subscript notation to describe a7.
A. a7 = -5
B. a7 = -1
C. a7 = -9
D. a7 = -4
To find the pattern in the sequence, we can observe that each term is obtained by subtracting 4 from the previous term. We start with 19 and subtract 4 to get 15, then subtract 4 from 15 to get 11, and so on.
Using subscript notation, we can represent each term as $a_n$, where $n$ represents the position in the sequence. Thus, we have:
$a_1 = 19$
$a_2 = a_1 - 4 = 19 - 4 = 15$
$a_3 = a_2 - 4 = 15 - 4 = 11$
$a_4 = a_3 - 4 = 11 - 4 = 7$
$a_5 = a_4 - 4 = 7 - 4 = 3$
Following this pattern, we can find $a_7$ by subtracting 4 from $a_6$:
$a_7 = a_6 - 4$
However, since we are only given the first 5 terms, we need to determine the value of $a_6$.
Starting with $a_5 = 3$, we subtract 4 to find $a_6$:
$a_6 = a_5 - 4 = 3 - 4 = -1$
Finally, we can find $a_7$ by subtracting 4 from $a_6$:
$a_7 = a_6 - 4 = -1 - 4 = \boxed{\text{(C) } -9}$