1. ## Factoring by grouping

Can anyone help me with the problem below:

Factorise fully the following expression:
8ax + 40cx + 3a +18c

I am told that I need to group the terms with common factors (i.e a's and c's) however when these are grouped there is no HCF between the associated numbers.

I'm sure I've missed something pretty fundamental but I just cant see it.

Any help would be great.
Thanks

2. ## Re: Factoring by grouping

I would NOT try grouping "a's and c's". The first thing I would try would be grouping as (8a+ 40c)x+ (3a+ 18c)= 8(a+ 5c)x+ 3(a+ 5c)= (a+ 5c)(8x+ 3).

3. ## Re: Factoring by grouping

Originally Posted by Simonamf
Factorise fully the following expression:
8ax + 40cx + 3a +18c
... I would try would be grouping as (8a+ 40c)x+ (3a+ 18c)= 8(a+ 5c)x+ 3(a+ 5c)= (a+ 5c)(8x+ 3).
That factorization yields 15c vice 18c ... ?

4. ## Re: Factoring by grouping

Ouch! You mean "18" is not equal to "15"?

5. ## Re: Factoring by grouping

Originally Posted by skeeter
That factorization yields 15c vice 18c ... ?
I thought that too much easier than the answer I was getting... Possibly a typo in the OP?

-Dan