If you could offer some help please (1 Viewer)

[BraydenGay]

Hi, I was just doing past papers today and I came across this loan repayments question. The problem isn't the question itself, it's the solution in the book.

It factorises: (3 x 10^6)(1.12^n) - (4 x 10^6)(1.12^n) + (4 x 10^6)

into: =(1.12^n)[(3 x 10^6)-(4 x 10^6)] + (4 x 10^6)

which is fine, and dandy but then it minuses the two things it factorises and makes:

= (4 x 10^6) - (1 x 10^6)(1.12^n)

and I thought that you couldn't do that. It seems like a fundamental thing I have forgotten, like from back in year 9...

Sorry if this sounds really stupid, rightly so. But i'm really confused. The only thing I can think of is that i'm thinking of factorising algebraic terms like:

x^2 + 2x +3
=(x-3)(x+1)

and that the reason you can't do that same thing is because you can't subtract x by 3 because x is an expression, but you can do it when they're just numbers like in the loan repayments?


thanks

 

[tacogym27101990]

3x10^6 - 4x10^6 - -1 X 10^6

 

[munchiecrunchie]

or if its easier to visualise it this way,

3 000 000 - 4 000 000 = -1 000 000 = -1 x 10^6

 

[veloc1ty]

Yeah if you didn't realise from the two posts above: they're actually expanding the brackets, it's not factorisation. Very good idea to get used to full working out so you don't make mistakes.

 

[BraydenGay]

oh right...

grr i'm such an idiot, I understand what they've done now, thank you all.