+2669 Let a_1, a_2, a_3, \dots be a sequence. If
a_n = a_{n - 1} + a_{n - 2}
for all n \ge 3, and a_{11} = 4 and a_{10} = 1, then find a_6.
+399 \(a_n = a_{n - 1} + a_{n - 2}\)
\(a_{n-2}=a_n-a_{n-1}\)
\(a_9=4-1=3\)
\(a_8=1-3=-2\)
\(a_7=3-(-2)=5\)
\(a_6=-2-5=-7\).
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