tonebeeze wrote:Sequence A(n) is defined as follows:
A(1) = 5 ;
A(n) = A(n-2) + A(n-1)
If A(5) = 7 what is A(2)?
a. -3
b. -1
c. 1
d. 2
e. 3
We can plug in the answers for A(2).
Answer choice C: A(2) = 1
A(3) = A(1) + A(2) = 5+1 = 6.
A(4) = A(2) + A(3) = 1+6 = 7.
Since A(5) = 7, answer choice C is too big. Eliminate C, D and E.
Answer choice B: A(2) = -1
A(3) = A(1) + A(2) = 5+(-1) = 4.
A(4) = A(2) + A(3) = -1+4 = 3.
A(5) = A(3) + A(4) = 4+3 = 7. Success!
The correct answer is
B.
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