Questions concerning adjectives

[sparky]

Well, I sort of know how some adjectives link together (see below), but I would like it if somebody could help me with these few questions? Please, anybody? I'll be forever gratetful!

- How do I join sentences with NON-PAST & NEGATIVE adjectives?
- How do I join sentences with PAST (both POSITIVE & NEGATIVE) adjectives?
- My teacher told me you can't use this if you'd like to say opposite characteristics about something/somebody (you'd have to use other sentence structures, like adding [kedo] and such). What I'd like to know is how can you say that a certain object/person is, for example, "dirty and not pretty"? After all, they are both negative in meaning, but one word is written in the positive form and the other, in the negative.

Thanks in advance! I hope I was able to make myself understood! ^__^

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NON-PAST & POSITIVE
[i] adjectives
> take away the [i] at the end and add a [kute].
Ex.: atarashii --> atarashikute
Sentence: kono hon wa atarashikute, omoshiroi desu.
(This book is new and interesting.)

[na] adjectives
> just add [de].
Ex.: genki --> genki de
Sentence: ano hito wa genki de, wakai desu.
(That person is enertic and young.)

[CviCvraeVtMoriar]

[EDIT]
I do not know to what extent this will be utterly replete with errors and mistakes and instances of misinformation; I did not sleep last night, and, so, can not be liable - particularly as I am now giving you this caveat - for any trouble into which you may get yourself on account of having taken these things to heart. (It's now 5:23 P.M., so I haven't slept in 33 1/2 hours... )
[/EDIT]

sparky wrote:
- How do I join sentences with NON-PAST & NEGATIVE adjectives?

この映画は面白くなくて、　特に教育的じゃない。
This movie isn't interesting, and it's not particularly educational.

ない is just another adjective, and you already know how to put those in a 'syndetic' or 'copulatory' form...

sparky wrote:
- How do I join sentences with PAST (both POSITIVE & NEGATIVE) adjectives?

Ya' don't. The tense of the adjective in the subordinated clause is determined by the tense of the leading verb, the verb of the primary clause:

この映画は面白くなくて、　特に教育的じゃなかった。
This movie wasn't interesting, and it wasn't particularly educational.

この本は有益で、　その上、 面白かったよ。
This book was beneficial, and, what's more, interesting.

sparky wrote:
What I'd like to know is how can you say that a certain object/person is, for example, "dirty and not pretty"? After all, they are both negative in meaning, but one word is written in the positive form and the other, in the negative.

With respect to "dirty" and "not pretty", one may be positive grammatically, and the other negative grammatically; however, they are not opposed in meaning, thus, you can use the two in the construction with which you are apparently already familiar:

あの女の子は汚くて、　奇麗じゃなくもある。　？ (I am fairly certain that this will sound quite weird.)

[sparky]

Thank you, thank you, thank you SO very much, CviCvraeVtMoriar! I'll be able to sleep peacefully tonight! *lol* (Speaking of which, 33 1/2 of no sleep?! Go sleep! ^__^ You're gonna sleep like a baby, since that tends to happen to whom hasn't slept in so long! Lucky you!)

CviCvraeVtMoriar wrote:
ない is just another adjective, and you already know how to put those in a 'syndetic' or 'copulatory' form...

Does that mean that in the case of a negative [na] adjective, we have what follows? (Both in informal and formal conversation?)
kirei ja nai --> kirei ja nakute

Once again, though, arigatou gozaimasu!