I thought I've mastered this but I'm getting confused again.

I thought the ~く form of i-adjectives was used when the adjective modifies the
noun, e.g.

> 新しく家を買う
>
> 難しく試験した

I think it's named "continuative form" but I'm not sure

Am I correct?. If not, please explain me the correct use.

PS. I think the examples are correct if not please correct me.
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2015-08-01T18:47:30.433
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2018-09-26T03:47:52.733
2020-06-17T08:18:27.500
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grammar i-adjectives
～く form of i-adjectives
No, the i-adjectives modify the noun in the attributive form (連体形) (which
looks like the "dictionary form")

> 新しい家を買う  
>  to buy a new house

When you know more Japanese, this becomes easy to remember, because both verbs
and i-adjectives modify nouns this way

> 家を買う人  
>  a person, who buys a house  
>  "a house-buying person"

The ～く form of the i-adjective functions like an adverb, so

> 新しく家を買う

would mean something more like

> to buy a house again/anew

* * *

Accordingly, your second example should be

> 難し **い** 試験を受けた。  
>  I took a difficult test.
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2015-08-01T19:15:27.577
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The く form is used to modify verbs not nouns.

For example take the adjective 速い{はやい｝ which means 'to be fast'. In this form
it is used to modify nouns as in 速い犬{いぬ｝ (a fast dog). But, when in the く form
it modifies verbs as in 速く走る{はしる} (to run quickly).

When you come to study na-adjectives you'll find a similar change required.
na-adjectives need な to modify a noun, but take に to modify a verb. For
example take the na-adjective きれい 'to be pretty' (not an i-adjective despite
ending in い). You would say きれいな犬 (a pretty dog), but きれいに書く{かく} (to write
prettily).
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2015-08-01T19:32:58.380
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2015-08-01T19:45:33.107
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> 早｛はや｝く新｛あたら｝しい家｛いえ｝を買｛か｝ったほうがいいですよ。

Hayaku atarashii ie wo katta hou ga ii desu yo.

It is better to buy a new home soon.

  * 早｛はや｝く is an adverb to modify a verb 買｛か｝った, while
  * 新｛あたら｝しい is an adjective to modify a noun 家｛いえ｝.
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2015-08-02T01:41:31.690
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In English, we could attach the suffix “ly” to the adjective to make it an
adverb. For example, adding “ly” to the end of “beautiful”, we get
“beautifully” which is an adverb. Why do we do this “trick, you may ask. The
reason is that adjective can modify nouns, but it can not modify verbs. You
could say “She is a beautiful girl”, but you couldn’t say “She sings
beautiful”. You need to change “beautiful” to “beautifully” if you want to
modify the verb “sing”. In Japanese, the way to change a I-adjective to adverb
is drop the “i” and add “ku”. To change a na-adjective, you drop the “na” and
add “ni”.
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2018-09-26T03:47:52.733
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