Turn on thread page Beta

    The sixth term of an arithmetic sequence is equal to twice the the fourth term, and the tenth term equals 48. find the first term "a" and the common difference "d":

    here goes:
    6th term = 2 * (4th term)
    4th term = a + 3d
    6th term = 2 (a + 3d)
    so, 6th term = 2a + 6d

    10th term = a + 9d = 48

    help!! i got to this part. i was thinking to simultaneously solve the 2 equations to find "a" and "d", but i dont have an actual value for the 6th term. i only know that the 10 term is 48. please help someone!!
    Offline

    0
    ReputationRep:
    (Original post by Meander)
    The sixth term of an arithmetic sequence is equal to twice the the fourth term, and the tenth term equals 48. find the first term "a" and the common difference "d":

    here goes:
    6th term = 2 * (4th term)
    4th term = a + 3d
    6th term = 2 (a + 3d)
    so, 6th term = 2a + 6d

    10th term = a + 9d = 48

    help!! i got to this part. i was thinking to simultaneously solve the 2 equations to find "a" and "d", but i dont have an actual value for the 6th term. i only know that the 10 term is 48. please help someone!!
    The 6th term is a+5d.

    lol..........ohh my god i am so thick. how on earth did i make such a mistake. well, i am really stuck now, please can someone help!!!
    Offline

    18
    ReputationRep:
    (Original post by theone)
    The 6th term is a+5d.
    Why 5d?
    Offline

    0
    ReputationRep:
    (Original post by ZJuwelH)
    Why 5d?
    Because it's the 6th term.
    Offline

    0
    ReputationRep:
    (Original post by Meander)
    lol..........ohh my god i am so thick. how on earth did i make such a mistake. well, i am really stuck now, please can someone help!!!
    a+5d = 2a + 6d. So a+d = 0.
    Offline

    18
    ReputationRep:
    (Original post by theone)
    Because it's the 6th term.
    Oh yeah. Been a while.
    Offline

    18
    ReputationRep:
    (Original post by theone)
    a+5d = 2a + 6d. So a+d = 0.
    So a=-d and a+9d = 48 so 8d=48 >>> d=6 and go from there.
    That right theone?
    Offline

    0
    ReputationRep:
    I don't know if this is right, if it is, I am Jesus

    a+3d = 2a+6d

    0=a+3d
    48=a+9d

    6d=48 d =8

    a+ 9(8) = 48
    a+72 = 48
    a=48-72 = -24

    test - a+3d =2a + 6d
    -24 + 24 = -48 + 48
    0 = 0 its correctamundo
    Offline

    0
    ReputationRep:
    (Original post by gayboy09)
    I don't know if this is right, if it is, I am Jesus

    a+3d = 2a+6d

    0=a+3d
    48=a+9d

    6d=48 d =8

    a+ 9(8) = 48
    a+72 = 48
    a=48-72 = -24

    test - a+3d =2a + 6d
    -24 + 24 = -48 + 48
    0 = 0 its correctamundo
    The first line is wrong
    Offline

    0
    ReputationRep:
    On this instant you should ignore gayboy09, his maths is as rusty as a nail that is rusty.
    Offline

    18
    ReputationRep:
    (Original post by gayboy09)
    On this instant you should ignore gayboy09, his maths is as rusty as a nail that is rusty.
    ... Just on this instant?

    ahhh, i see it. we find two expressions for the 4th and 6 th term, we then cancel this to give us an equation. we tthen use this equation and solve it simultaneoulsy with: 10 term = a + 9d = 48 to find a and d:

    a + d = 0
    a + 9d = 48

    -8d = 48
    d = 48/(-8)
    d = -6

    sub d=-6 back into a+d = 0:

    a + (-6) = 0
    so a = 6

    therefore the first term ("a") = 6
    the common difference = -6

    hooray!!!!!!!

    where on earth did you guys get d = 8 from? you are using the wrong equation, you are using a + d =0. where did this 3d come from? i got the right answer coz my answer sheet says so. you did it wrong some of you guys
    Offline

    18
    ReputationRep:
    (Original post by meander)
    ahhh, i see it. we find two expressions for the 4th and 6 th term, we then cancel this to give us an equation. we tthen use this equation and solve it simultaneoulsy with: 10 term = a + 9d = 48 to find a and d:

    a + d = 0
    a + 9d = 48

    -8d = 48
    d = 48/(-8)
    d = -6

    sub d=-6 back into a+d = 0:

    a + (-6) = 0
    so a = 6

    therefore the first term ("a") = 6
    the common difference = -6

    hooray!!!!!!!
    Actually -8d=-48, so d=6 and a=-6.

    lol, oops tes, i was rushing a bit there. when i did the question on paper i did it correctly as you said...........i just typed it too fast...
    Offline

    18
    ReputationRep:
    (Original post by Meander)
    lol, oops tes, i was rushing a bit there. when i did the question on paper i did it correctly as you said...........i just typed it too fast...
    <thumbs up> We got there at least!
    Offline

    1
    ReputationRep:
    I would answer, but I'm off to bed. Night all.
    Offline

    18
    ReputationRep:
    (Original post by Bhaal85)
    I would answer, but I'm off to bed. Night all.
    <the no-vavavoom face> Dude you said that an hour ago.
    Oh well I'm off too. See y'all tomorrow!
 
 
 
Turn on thread page Beta
Updated: November 8, 2003

University open days

  • University of Exeter
    Undergraduate Open Days - Exeter Campus Undergraduate
    Wed, 24 Oct '18
  • University of Bradford
    Faculty of Health Studies Postgraduate
    Wed, 24 Oct '18
  • Northumbria University
    All faculties Undergraduate
    Wed, 24 Oct '18
Poll
Who is most responsible for your success at university
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

Equations

Best calculators for A level Maths

Tips on which model to get

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.