Quadratic equation question help plz

Announcements Posted on
Four things that unis think matter more than league tables 08-12-2016
    • Thread Starter
    Offline

    2
    ReputationRep:
    2x^4+14x^2+24
    I got one solution but I don't know why the other solution is supposed to be 2(x^2+3) when I divided the equation by 2 at the beginning please help.Name:  image.jpg
Views: 18
Size:  508.9 KB
    Offline

    3
    ReputationRep:
    I can't tell what the question is
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by CorpusLuteum)
    I can't tell what the question is
    its at the top
    Offline

    3
    ReputationRep:
    (Original post by p29)
    its at the top
    Is the quadratic equal to zero.
    Are you only finding x? Why is there a Y.
    Be more clear.
    Online

    3
    ReputationRep:
    (Original post by p29)
    2x^4+14x^2+24
    I got one solution but I don't know why the other solution is supposed to be 2(x^2+3) when I divided the equation by 2 at the beginning please help.
    As above, be more clear.

    Are you solving 2x^4+14x^2+24=0??? Or are you rearranging for something?

    You let y=x^2 got up to (y+3)(y+4)=0 which is almost correct.

    So y=-3 or y=-4

    Hence x^2=-3 or x^2=-4

    Which gives you complex roots.
    Offline

    2
    ReputationRep:
    (Original post by p29)
    its at the top
    You're overcomplicating it - the solution should only really be three lines max.
    Start with the equation, divide by 2, factorise it (as (x^2+a)(x^2+b) of course) and then solve. Just because the quadratic is in x^2 as opposed to x doesn't mean you can't solve it in the normal way.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by RDKGames)
    As above, be more clear.

    Are you solving 2x^4+14x^2+24=0??? Or are you rearranging for something?

    You got up to (y+3)(y+4)=0

    So y=-3 or y=-4

    Hence x^2=-3 or x^2=-4

    Which gives you complex roots.
    =0 and I have to factorise it
    Online

    3
    ReputationRep:
    (Original post by p29)
    =0 and I have to factorise it
    If you have to factorise it then you've already done it with the y's, so replace them with x2 and you're done.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by p29)
    =0 and I have to factorise it
    the book says that when it is factorised one of them will be 2(x^2+3) which i dont understand
    • Thread Starter
    Offline

    2
    ReputationRep:
    ????
    • Thread Starter
    Offline

    2
    ReputationRep:
    is the book wrong?
    Offline

    2
    ReputationRep:
    Okay what factorisation have you got so far?
    Online

    3
    ReputationRep:
    (Original post by p29)
    is the book wrong?
    No. You have factored out a 2 at the start so you need to bring it back.
 
 
 
Write a reply… Reply
Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: September 18, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Poll
Do you think you'll achieve your predicted A Level grades?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read here first

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.