# Thread: help with some maths

1. ## help with some maths

I have a brain fade moment with the following equation that I need to factorise by extraction and grouping of a commom factor

15a - 6b - 5ax + 2bx

Thanks

2. I think you need the other side of the equation - is this =0, or =y (so then you have four variables).

Assuming latter (you can always substitute in then:

a= (y +b(6-2x))/(15-5x)

3. b=(y+a(5x-15))/(2x-6)

4. x= (y-15a+6b)/(2b-5a)

Does this answer your question? If you need to remove the variables further, you can substitute one of the variables with the equation that is it's subject and simplify.....

5. still confused

one of the others I have is

5x^4 - 3x^3 + 4x^2 which I have worked out to x^2(5x^2 - 3x +4) with x^2 being the commom factor

6. 15a - 6b - 5ax + 2bx

to factor
-(5a-2b)(x-3)

I think,it's been a while

if its factor by grouping i would say
(3-x)(5a-2b)

7. .....so ..... I *think* I'm down to 2y=x^2-4bx+12b. And now having brain fade myself on the quadratic. Should come out as something like 2y= (x-6b)(x+2b) - but that gives -12b at the end (not plus)

am I helping, or making things worse?!

8. Gelerts factorisation works out....

Your second factorisation also looks fine - you can probably break down the quadratic a little further too - again, I'm struggling with that.

9. What are you actually trying to achieve?

10. 5x^4 - 3x^3 + 4x^2

to factorise

5x4-3x3+4x2

greatest common factor
x2(4+-3x+5x2)

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