Hey there! Sign in to join this conversationNew here? Join for free
Turn on thread page Beta
    • Thread Starter
    Offline

    3
    ReputationRep:
    So i need to factorise 2x^2+13x+15

    The way Ive been taught is 2 x 15 is 30, then use factors of 30.
    All the calculators for this say the factors you use are 3 and 10 but they dont add up into 15

    Where am I going wrong?
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Peterson957)
    So i need to factorise 2x^2+13x+15

    The way Ive been taught is 2 x 15 is 30, then use factors of 30.
    All the calculators for this say the factors you use are 3 and 10 but they dont add up into 15

    Where am I going wrong?
    ax^2+bx+c

    The two numbers you're looking for should multiply to give a\times c and add to give b.

    So in this case, the two numbers should add multiply to give 30 and add to give 13.
    Offline

    18
    ReputationRep:
    (Original post by Notnek)
    ax^2+bx+c

    The two numbers you're looking for should multiply to give a\times c and add to give b.

    So in this case, the two numbers should add multiply to give 15 and add to give 13.
    I think you mean

    So in this case, the two numbers should add multiply to give 30 and add to give 13.
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by DFranklin)
    I think you mean
    Thanks, that was an unfortunate mistake.

    Peterson957 Sorry if that confused you. I've edited my post now.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: October 3, 2017
Poll
“Yanny” or “Laurel”
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

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