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

Method of factorising quadratics when coefficient is greater than 1?

    • Thread Starter
    Offline

    1
    ReputationRep:
    Hey, I was just wondering if there is an easy method of factorising quadratics when the coefficient is greater than 1. For example, 1 question is 6x^2-11x-7=0. In school, we are just taught to do it in our heads but on questions like this it gets hard so I want to know a written method of solving this sort of questions

    Thanks.
    Offline

    2
    ReputationRep:
    AC= 6*-7= -42
    something that multiplys to get -42 but adds to get -11
    = -14 +3 = -11
    =-14 x 3 =-42
    new equation = 6x^2-14x+3x-7
    (6x^2-14x)+(3x-7)
    factorise (both brackets must be equal)
    (6x^2-14x)+(3x-7)
    Offline

    2
    ReputationRep:
    2x(3x-7) + (3x-7)
    (3x-7) (2x+1) ?
    not sure if its plus one in last bracket though
    Offline

    3
    ReputationRep:
    You can always plug the numbers into the quadratic solution to get the roots directly, then back out the brackets that way.

    E.g.

    x = 7/3 and -1/2, from the general quadratic equation solution

    so the factors must be (3x - 7) and (2x + 1)

    i.e. when these factors are zero, x equals the answers we calculated.
 
 
 
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.