276698
Similarly : Then the zeroth - and first-order problems of the multiple-scales perturbation series for the Duffing equation become : Solution The zeroth-order problem has the general solution : with A ( t1 ) a complex-valued amplitude to the zeroth-order solution Y0 ( t , t1 ) and i2 = − 1 .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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