C4 vectors doubt.... please help!

hello,

If the question has given me OA= (5j+5k) and OB=(3i+2j-k) and asked to write the vector equation of the line that passes through these 2 points, I wrote:
r=(5j+5k)+t(3i-3j-6k)

but in the marking scheme, the (3i-3j-6k) part is written as (i-j-2k) only.
why don't we write it as 3(i-j-2k) because 3 is the multiple right?

Any help will be greatly appreciated!

Either answer is fine since the direction vector can be any vector parallel to the line - there are infinitely many ways you can write the vector equation of a line. The mark scheme will only give one answer but may say something like "or equivalent".

To make later working simpler it can be a good idea to write the direction vector as simply as possible like the mark scheme has done. But there's the risk that you may make a mistake in doing this