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In "宿題をしなくてはいけなかった" meaning "Had to do homework.", is the word "いけなかった" derived from "いける" (verb conjugation) or from "いけない" (i-adjective conjugation)?

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possible duplicate of japanese.stackexchange.com/questions/3765/… – cypher Apr 25 '12 at 23:30
@cypher I'm not sure. It doesn't seem like the same question to me. – ジョン Apr 25 '12 at 23:47
@ジョン maybe not, but I think it's pretty similar. It does explain ~なくてはいけない if not ~なくてはいけなかった. – cypher Apr 25 '12 at 23:54
@cypher That's true, the asker would definitely find that question very helpful. This question would be better phrased as a general question about the behaviour of negative/past tense verbs, since that seems to be what's causing the confusion. My answer is probably inadequate but I'm not quite sure where to start. – ジョン Apr 26 '12 at 0:10
Might wanna take a look at japanese.stackexchange.com/questions/4746/… as well. – dainichi Apr 26 '12 at 1:25
up vote 1 down vote accepted

It's the past form of いけない, which in turn is the negative form of いける:

  • いける (plain)

  • いけない (negated)

  • いけなかった (negated-past)

Like with any verb, the negative form of いける behaves like an い-adjective.

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