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

Factorising help needed Watch

    • Thread Starter
    Offline

    2
    ReputationRep:
    What is
    8x^2-30x-27 factorised please?
    Thanks
    • Community Assistant
    Offline

    3
    ReputationRep:
    Hello I have moved both of your threads to the maths forum.

    We do not provide full solutions in this forum, please post attempts of both of the questions and then we will help you from there.
    Offline

    2
    ReputationRep:
    Basically you're looking for a solution in the form (ax+b)(cx+d), where a, b, c, and d are all integers (i.e. they could be negative). Multiplying (ax+b) by (cx+d) should result in your original expression. So think about how a, b, c, and d are related to the coefficients in your expression - that is, how they produce 8, -30, and -27.
    Offline

    3
    ReputationRep:
    it's not so difficult

    start with the 27 - the only way to get 27 is to multiple 9 and 3 or 27 and 1(one of which will be negative as it's -27)

    so now you know you have (ax +/- 9)(bx +/- 3) or (ax +/- 27)(bx +/- 1)

    if you're going to have 8x^2 then axb = 8... so your options are 8x and 1x (8x x 1x = 8x^2) or 2x and 4x (2x x 4x = 8x^2)

    so to find out what you use just play around and try the different possibilities (or use some logic)
 
 
 
Poll
Is GoT overrated?
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.