Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    I need to make V1 the subject and im having trouble progressing with it

    V1-Vs2/R1 + V1/R2 - IS = 0

    I started doing this, is this correct?

    R2V1 - R2VS + R1V1 / R1R2 = IS
    Offline

    15
    ReputationRep:
    (Original post by lcuckstudent)
    I need to make V1 the subject and im having trouble progressing with it

    V1-Vs2/R1 + V1/R2 - IS = 0

    I started doing this, is this correct?

    R2V1 - R2VS + R1V1 / R1R2 = IS
    you need to use brackets so that the question is more clear because the way that you have written the question could mean a different few things
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by B_9710)
    you need to use brackets so that the question is more clear because the way that you have written the question could mean a different few things
    (V1-Vs2 / R1)+ (V1 / R2)- (IS)= 0

    (R2V1 - R2VS + R1V1)/ (R1R2)= IS

    Does this help
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by lcuckstudent)
    (V1-Vs2 / R1)+ (V1 / R2)- (IS)= 0

    (R2V1 - R2VS + R1V1)/ (R1R2)= IS

    Does this help
    I have attached a picture instead
    Attached Images
     
    Offline

    15
    ReputationRep:
    All that you have done so far seems to be correct.
    Offline

    15
    ReputationRep:
    (Original post by lcuckstudent)
    I have attached a picture instead
    Now multiply both sides of the equation by r1r2 and then try and see if you can take out v1 as a common factor which will allow you to further manipulate the equation and make v1 the subject of the equation.
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by B_9710)
    Now multiply both sides of the equation by r1r2 and then try and see if you can take out v1 as a common factor which will allow you to further manipulate the equation and make v1 the subject of the equation.
    I think I may have run away with it to much
    Attached Images
     
    Offline

    15
    ReputationRep:
    (Original post by lcuckstudent)
    I think I may have run away with it to much
    You're right. Now all you need to do is divide by sides by the (r2+r1) and then that's the answer.
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by B_9710)
    You're right. Now all you need to do is divide by sides by the (r2+r1) and then that's the answer.
    Thats what I thought but I have been told the answer is the one attached
    Attached Images
     
    Offline

    15
    ReputationRep:
    (Original post by lcuckstudent)
    Thats what I thought but I have been told the answer is the one attached
    It is exactly the same answer. The answer that you got originally though is in a much nicer form. You can easily show that these 2 fractions are identical.
    Offline

    15
    ReputationRep:
    Name:  image.jpg
Views: 49
Size:  486.0 KB
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by B_9710)
    It is exactly the same answer. The answer that you got originally though is in a much nicer form. You can easily show that these 2 fractions are identical.
    So my final outcome would be the one attached. But when I give the unknown variables a value, the results are not the same as the one I was told was correct
    Attached Images
     
    Offline

    15
    ReputationRep:
    (Original post by lcuckstudent)
    So my final outcome would be the one attached. But when I give the unknown variables a value, the results are not the same as the one I was told was correct
    It doesn't look like you have factorised the numerator correctly. You can only take out a factor of r2 on the numerator.
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by B_9710)
    It doesn't look like you have factorised the numerator correctly. You can only take out a factor of r2 on the numerator.
    so your saying:

    Is*R1*R2+R1*Vs

    Cant be:

    Is*R1(R2+Vs)

    ???
    Offline

    15
    ReputationRep:
    (Original post by lcuckstudent)
    so your saying:

    Is*R1*R2+R1*Vs

    Cant be:

    Is*R1(R2+Vs)

    ???
    Yes because Is*R1 is not common to both. You could take out a factor of R1 giving R1(Is*R2 + Vs)
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by B_9710)
    Yes because Is*R1 is not common to both. You could take out a factor of R1 giving R1(Is*R2 + Vs)
    But R1 is common to both R2 and Vs is it not im confused
    Offline

    15
    ReputationRep:
    (Original post by lcuckstudent)
    But R1 is common to both R2 and Vs is it not im confused
    R1 is common. But Is*R1 is not common to both which is what you originally did when you posted the picture.
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by B_9710)
    R1 is common. But Is*R1 is not common to both which is what you originally did when you posted the picture.
    oh right yeah sorry I can see now!!!!

    I think its getting late for me, thanks again for your help
    Offline

    15
    ReputationRep:
    Ok I've posted it all stow by step because it appears we have both lost our way with this one so I'll just do it from the start. Name:  image.jpg
Views: 56
Size:  480.5 KB
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by B_9710)
    Ok I've posted it all stow by step because it appears we have both lost our way with this one so I'll just do it from the start. Name:  image.jpg
Views: 56
Size:  480.5 KB
    Yea great now when I plug this one and the other one with numbers they come out the same
 
 
 

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.