help factorise (1 Viewer)

[_kuroo]

im not interested in the answer really. i just forgot how to factorise this:

a^2+12ac-28c^2
(i know the answer is (a-2c)(a+14c) )

whats the process of doing it?

 

[funnytomato]

i found it quite surprising that many ppl dislike the cross method

 

[RealiseNothing]

You just find two number that numbers that multiply to give -28c^2 and add to give 12c.

Although, for these type of questions, you really only need to find two numbers that multiply to give -28 and add to 12. This is because c times c gives you c^2, and when adding to numbers that have a c in them (ac + bc), the term still is only 'c'. So you just times the two numbers by 'c'.

Hence 14*-2=-28 and 14-2=12

So the numbers are 14 and -2, and you just times both by 'c'. So 14c and -2c. Answer is (a-2c)(a+14c).

 

[_kuroo]

ohhhh. thanks bro!!!!