たかく　ありませ or たかくないです??
I am working with 2 different textbooks to learn Japanese. In these two books I have sor far found the following 3 ways of making an adjective negative:

これは　あまり　たかい　くるま　じゃありません。
この　くるまは　あまり　たかく　ありません。
この　くるまは　たかくないです。

So what is the difference between the three? When would I use what?

Thanks. :-)

Question

たかく　ありませ or たかくないです??
I am working with 2 different textbooks to learn Japanese. In these two books I have sor far found the following 3 ways of making an adjective negative:

これは　あまり　たかい　くるま　じゃありません。
この　くるまは　あまり　たかく　ありません。
この　くるまは　たかくないです。

So what is the difference between the three? When would I use what?

Thanks. :-)

Answer

First one: This is not a really expensive car. 
Second one: This car is not really expensive.
Third one: This car is not expensive. (slightly less formal than number 2)

2 and 3 are almost exactly the same, just like I said, number 3 is a little less formal.

Number 1 is the only one that's really different and it's just a different way of phrasing it. Like in English you can say "This coffee is hot", or "This is hot coffee". In your first example you are using the adjective to describe the noun and then negating the noun, so it's not really making the adjective negative.