Let y=∑ n=0
[infinity]
​
c n
​
x n
. Substitute this expression into the following differential equation and simplify to find the recurrence relations. Select two answers that represent the complete recurrence relation. 2y ′
+xy=0 c 1
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=0 c 1
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=−c 0
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c k+1
​
= 2(k−1)
c k−1
​
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,k=0,1,2,⋯ c k+1
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=− k+1
c k
​
​
,k=1,2,3,⋯ c 1
​
= 2
1
​
c 0
​
c k+1
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=− 2(k+1)
c k−1
​
​
,k=1,2,3,⋯ c 0
​
=0