Turn on thread page Beta
    • Thread Starter
    Offline

    1
    ReputationRep:
    OK, this has took up most of my evening as I can't see where I'm going wrong. I'm able to solve for B1 and C1, but then when trying to solve equations 3 and 4 I am continually coming up with answers that actually only satisfy equation 3??

    I'll start from the beginning as B1 and C1 are irrational and the numbers worked with are quite small.

    1) -0.1B_1C_1 + \frac{0.01}{14000} - \frac{C_1}{1400} = 0

    2) 1.2625B_1C_1 - 0.00001B_1 - \frac{B_1}{1400} = 0

    Which are solved [by solving for C1 in (2) and subbing into (1)] to give:

    B1 = 0.005308...
    C1 = 0.00057369...

    Then,

    3) -0.1B_2C_2 + \frac{C_1}{700} - \frac{C_2}{700} = 0

    4) 1.2625B_2C_2 - 0.00001B_2 + \frac{B_1}{700} - \frac{B_2}{700} = 0

    I have pages of working on the last two and I'm getting nowhere! Please someone come along and tell me I'm missing something simple! :o: Thankyou!
    Offline

    6
    ReputationRep:
    Well that was fun.....sort of.

    B1=1507/283920 C1=507/883750

    Same values as I had hours ago....checked them and thought I was wrong. I'm too tired for this sort of thing. I keep making stupid mistakes.

    If it's any help, what I did was replace all the numbers with extra letters to simplify the algebra.

    With
    a=-1/10
    d=1/1400000
    e=-1400
    f=101/80
    g=-1/100000-1/1400

    B1=\frac{f}{age}(ed-\frac{g}{f}) and C1=ae(\frac{gB}{f}-\frac{d}{a})

    If you're missing something simple then so am I.

    I might try the other equations tomorrow.
    Offline

    6
    ReputationRep:
    Same approach for the second pair of equations led to a quadratic for B2.

    Not surprisingly I couldn't get exact values this time.

    I've got answers and they seem to check out ok.

    Spoiler:
    Show

    B2 = -0.0096363.......,C2 = 0.0017627.......

    and

    B2= 0.00781407....., C2 = 0.000370844......


    Let me know if you want any help.

    Chances are you just needed to do it with a fresh head like me.

    It was far easier after some sleep.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: November 9, 2008

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?
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.