O-Level Additional Math

[OK Lor]

Hi Sir,


The number of arrangement of the word BOOKS if both O are to be placed together.

Answer is 4!2! or 4!?

Thanks.

[Guan Hui]

4!2!=)

[OK Lor]

Hi Sir,


Thanks. You mean there are two arrangements of OO? shouldn't it be 2!/2!=1? since there are identical, confuse. How about the number of arrangements of AABB? 4!/(2!2!) or 4!?

Thanks.

[Guan Hui]

eh wrong de previous 1 should be 4! onli I am so sorry=)

1st question:
4! if you group OO together so BOKS.
den x 2! because OO can be swap
den / 2! because O same as O
so is 4!

2nd question
AABB
4! cause 4 alphabets
/ 2! cause 2 As
/2! cause 2 Bs
4!/2!2!=3!

[OK Lor]

Hi Sir,


Thanks for the clarification and kind help.

[Guan Hui]

sry for de wrong ans=) overlook it…

[hot_chocolate]

Hi, just asking, how do I factorise the following sums:


a) a^3 + b^3

b) x^5 + x + 1

Thanks!

[Guan Hui]

a) nothing can be done

b)x(x^4+1) +1??

[OK Lor]

a) (a+b)(a²-ab+b²)

[Guan Hui]

Hi OKlor,

NICE factorization there=)
nv thought of it.=)