Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    4
    ReputationRep:
    The curve y = 1 + ( 1 / 2+x) crosses the x axis at point A and the y axis at point B.

    (a) Calculate the coordinates of A and of B.

    Done this, they are A = (0, 1.5) and B = (-3, 0) checked the answer and this is correct

    (b) Find the equation of the line AB.

    Gradient of AB = y1-y2 / x1-x2 = 1.5-0 / 0-(-3) = 1.5/3 = 1/2

    Therefore y = 1/2 x + c

    Using (0, -3):
    -3 = 1/2 x 0 + c
    c = -3

    Thus

    y = 1/2 x - 3

    multiply all by 2 to remove fractions

    2y = x - 6

    this can be rearranged to

    x - 2y - 6 = 0

    I'm pretty sure this is correct. But the text book says the answer is x - 2y +3 = 0???

    What do you guys think?
    Offline

    13
    ReputationRep:
    its possible the txtbook is wrong....

    our chemistry one is full of them....get a few other people to work it out and if you all get the same answer...then assume its wrong
    Offline

    2
    ReputationRep:
    The answer is x-2y+3=0 since the coordinate you have chosen to use is (0, -3), where as you should have used (-3, 0) which you calculated in in part (a). It is just a simple error and your calculation is perfectly correct.
    Note: (0, -3) does not belong to the curve y = 1 + ( 1 / 2+x) which can be checked simply by substituting the values in to the equation.
    • Thread Starter
    Offline

    4
    ReputationRep:
    (Original post by RamsFanNo1)
    The answer is x-2y+3=0 since the coordinate you have chosen to use is (0, -3), where as you should have used (-3, 0) which you calculated in in part (a). It is just a simple error and your calculation is perfectly correct.
    Note: (0, -3) does not belong to the curve y = 1 + ( 1 / 2+x) which can be checked simply by substituting the values in to the equation.
    Thanks,

    I've been doing this so much (!

    Just started teaching myself maths again after being out of school for 3 yrs been doing c1 for about 4 days now. I get it and can do it but keep doing stupid stuff like that!!
    Offline

    2
    ReputationRep:
    (Original post by Bleak Lemming)
    Thanks,

    I've been doing this so much (!

    Just started teaching myself maths again after being out of school for 3 yrs been doing c1 for about 4 days now. I get it and can do it but keep doing stupid stuff like that!!
    Don't worry about it, we all make silly mistakes from tiem to time. To be honest it is good that you make these mistakes, because it is these which you will learn from and will not make again in the future. I wish you all the luck with learning A level maths and if you do ever have any problems, then feel free to ask me, I am always happy to help.
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?
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.