Competition problem — Algebra — Maths Olympiad Prep

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Algebra Difficulty 2.2 Junior Find the answer

In the sequence
$..., a, b, c, d, 0, 1, 1, 2, 3, 5, 8,...$
each term is the sum of the two terms to its left. Find $a$ :

Pick one

Solution

We work backwards to find $a$ .
$d+0=1\implies d=1$
$c+1=0\implies c=-1$
$b+(-1)=1\implies b=2$
$a+2=-1\implies a=\boxed{\textbf{(A)}-3.}$
--Solution by TheMaskedMagician

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