質問: past tense form verb + よかった と て form of verb + よかった はどう違いますか? past tense form verb + よかった と て form of verb + よかった はどう違いますか?
回答: 勉強したよかった is grammatically not correct. you can say 勉強したらよかった instead. 勉強してよかった = it was good that i studied. (= this person did study and he/she thinks that it was really good that he/she did it.) 勉強したらよかった = it would have been better if i had studied. / i should have studied. (= this person didn't study in reality.)