Join TSR now and get all your revision questions answeredSign up now

Equating Coefficients

    • Thread Starter
    Offline

    0
    ReputationRep:
    Hey I'm new!
    I've recently started my AS-levels and have not yet been taught Co-efficient equating...
    Here it is:

    By equating coefficients find A, B and C: 18. 𝑥2−𝑥≡𝐴𝑥(𝑥+1)+ 𝐵𝑥19. 𝑥−4≡𝐴(2−𝑥)+𝐵( −3)

    Name:  equating.jpg
Views: 68
Size:  19.5 KB
    If someone could help me with this I would really appreciate it!

    Thank you.
    Offline

    2
    ReputationRep:
    So, if , then:
    Equating coefficients of :
    Equating coefficients of :
    Equating coefficients of :
    Equating coefficients of :
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by metasysta)
    So, if , then:
    Equating coefficients of :
    Equating coefficients of :
    Equating coefficients of :
    Equating coefficients of :
    Okay so its mostly rearranging?

    My friend told me something about also solving it simultaneously.
    Offline

    3
    ReputationRep:
    (Original post by llamaha)
    Okay so its mostly rearranging?

    My friend told me something about also solving it simultaneously.
    It's not really rearranging so much. You basically expand everything on the RHS, collect the like terms (e.g. You would turn something like Ax+Bx^2+Cx into (A+C)x+Bx^2) and then you literally equate the coefficients and achieve equations which you can then solve. Some equations can have more than 1 variable for you to solve (such as the example I gave previously) therefore you would need another equation with the same unknowns in order to solve them simultaneously as your friend might've mentioned. This, of course, is not always the case as you would solve the single variable equations FIRST and see if you can use that information in double/triple/etc variable equations as well.

    So for 18, the RHS expanded fully would be Ax^2+(A+B)x and now you can compare the coefficients with LHS. As I previously mentioned, you can solve for the coefficient of x^2 first as that would give you the info you need for the coefficient of x
 
 
 
Poll
Which party will you be voting for in the General Election 2017?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

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

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.