Maths help cubic equation factorisation
hi I keep getting questions where I have to factorise a cubic equation, but how do you do it? Like I get it for quadratic but I just can't manage cubic, if anyone has a simple method I'd really appreciate it thx
for example:
f(x) = 2x^3 - 13x^2 + 8x + 48
and we know that (x-4) is a factor of f(x)
The mark scheme says the answer but doesn't explain it
(x-4)(2x^2 - 5x - 12)
for example:
f(x) = 2x^3 - 13x^2 + 8x + 48
and we know that (x-4) is a factor of f(x)
The mark scheme says the answer but doesn't explain it
(x-4)(2x^2 - 5x - 12)
(edited 1 year ago)
no I don't even know what that is lol
oh don't worry I'll try and watch a video but thank you for telling me about it 
Original post by purple_1710
hi I keep getting questions where I have to factorise a cubic equation, but how do you do it? Like I get it for quadratic but I just can't manage cubic, if anyone has a simple method I'd really appreciate it thx
for example:
f(x) = 2x^3 - 13x^2 + 8x + 48
and we know that (x-4) is a factor of f(x)
The mark scheme says the answer but doesn't explain it
(x-4)(2x^2 - 5x - 12)
for example:
f(x) = 2x^3 - 13x^2 + 8x + 48
and we know that (x-4) is a factor of f(x)
The mark scheme says the answer but doesn't explain it
(x-4)(2x^2 - 5x - 12)
This is a major topic that you should have been taught. Were you not taught a method and you are struggling with it? Or do you have no idea what to do?
Original post by purple_1710
hi I keep getting questions where I have to factorise a cubic equation, but how do you do it? Like I get it for quadratic but I just can't manage cubic, if anyone has a simple method I'd really appreciate it thx
for example:
f(x) = 2x^3 - 13x^2 + 8x + 48
and we know that (x-4) is a factor of f(x)
The mark scheme says the answer but doesn't explain it
(x-4)(2x^2 - 5x - 12)
for example:
f(x) = 2x^3 - 13x^2 + 8x + 48
and we know that (x-4) is a factor of f(x)
The mark scheme says the answer but doesn't explain it
(x-4)(2x^2 - 5x - 12)
Remember X = 2x-4/12
I've been taught in different countries so I think it's possible I may have skipped this topic somehow. I can manage to factorise it without the constant at the end, that number is what's bothering me
Original post by Notnek
This is a major topic that you should have been taught. Were you not taught a method and you are struggling with it? Or do you have no idea what to do?
Original post by purple_1710
I've been taught in different countries so I think it's possible I may have skipped this topic somehow. I can manage to factorise it without the constant at the end, that number is what's bothering me
Here are the two most common ways that it's taught:
https://www.youtube.com/watch?v=RIHqIjt9jy0
https://www.youtube.com/watch?v=XSsg9F_xeEY
ok thank u sm, I'll take a look at the videos and the drawing thank uuu
Just thought I'd chip in with some alternative videos that might be considered a bit lower level, but I found at gcse further maths were really useful .
On Factor Theorem (a precursor, why we use it in algebraic long division) - Factor Theorem
Algebraic Long Division (how we were taught it, synthetic division may be the proper name haha) - Algebraic Long Division
The videos Notnek left are epic (kudos), just thought I'd leave these as I thought they were also nice and concise, and have different questions you can practise and follow along with.
Good luck with your exams
!
. On Factor Theorem (a precursor, why we use it in algebraic long division) - Factor Theorem
Algebraic Long Division (how we were taught it, synthetic division may be the proper name haha) - Algebraic Long Division
The videos Notnek left are epic (kudos), just thought I'd leave these as I thought they were also nice and concise, and have different questions you can practise and follow along with.
Good luck with your exams
!Quick Reply
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