Turn on thread page Beta
    • Thread Starter
    Offline

    2
    ReputationRep:
    ive nevr encounted this kind of thing before help?? lool i have like 20mins before its due
    PLEASE HELP, LESSON IN 20MINS! ASNWERS WITH EXPLANATION IF U CAN!
    ( this sign '^' MEANS TO THE POWER)
    a) given that y=2^x find expressions in terms of y for,
    1)2^x+2

    2)2^3-x

    b) show that using y =2^x, the equation
    2^x+2 +2^3-x=33 can be rewritten as 4y^2-33y+87=0

    c) hence solve
    2^x+2 +2^3-x=33

    and lastly,
    f(x)=x^1/2 -8x^-1/2
    evaluate f(3) giving answer in simplest form with a rational denominator!

    Helpp! im gonna be eaten alive!!!
    Offline

    11
    ReputationRep:
    We're here to help you with any problems you have understanding topics, not do your work for you because you left it to the last minute.
    Offline

    17
    ReputationRep:
    (Original post by cheesecake11)
    ive nevr encounted this kind of thing before help?? lool i have like 20mins before its due
    PLEASE HELP, LESSON IN 20MINS! ASNWERS WITH EXPLANATION IF U CAN!
    ( this sign '^' MEANS TO THE POWER)
    a) given that y=2^x find expressions in terms of y for,
    1)2^x+2

    2)2^3-x

    b) show that using y =2^x, the equation
    2^x+2 +2^3-x=33 can be rewritten as 4y^2-33y+87=0

    c) hence solve
    2^x+2 +2^3-x=33

    and lastly,
    f(x)=x^1/2 -8x^-1/2
    evaluate f(3) giving answer in simplest form with a rational denominator!

    Helpp! im gonna be eaten alive!!!
    ai and aii equal to? ie 2^x+2 = 0
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by Phenomenological)
    We're here to help you with any problems you have understanding topics, not do your work for you because you left it to the last minute.
    jeez sorry, i was vomitting all weekend and i got it on friday so i couldnt really do it in between vomitting and coughing my guts out!
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by FranticMind)
    ai and aii equal to? ie 2^x+2 = 0
    i guess so, it doesnt say
    Offline

    11
    ReputationRep:
    (Original post by cheesecake11)
    jeez sorry, i was vomitting all weekend and i got it on friday so i couldnt really do it in between vomitting and coughing my guts out!
    Then tell the teacher that. Most of them do have the capacity for sympathy, though admittedly I've known a few who don't.
    Offline

    16
    ReputationRep:
    a) y=2^x so x=log (base2)y
    And substitute.
    i) is simple, but ii) is a logarithms question, I think, though b) implies it simplifies out.

    b) Same

    c) Solve equation for y (quadratic) and substitute=2^x

    f(3) - just use a calculator with 3 in place of x.
    Offline

    16
    ReputationRep:
    (Original post by cheesecake11)
    i guess so, it doesnt say
    It doesn't need an equal to bit - it's just a term that they want in terms of y (see above).

    Hope that helps in terms of method - I'll try working out the answers.
    Offline

    17
    ReputationRep:
    (Original post by cheesecake11)
    i guess so, it doesnt say
    Well its really simple substitution for a.i ? And then for a.ii you just rearrange the so you can substitute using logs.

    For b again just substitute in and a hint would be use power laws on the 2^3-x term (a^3)/(a^x) = a^3-x. Then for c just simple quadratic that you made.

    The last part is easy just put 3 in as the x and simplify.
    Offline

    17
    ReputationRep:
    (Original post by Octohedral)
    a) y=2^x so x=log (base2)y
    And substitute.
    i) is simple, but ii) is a logarithms question, I think, though b) implies it simplifies out.

    b) Same

    c) Solve equation for y (quadratic) and substitute=2^x

    f(3) - just use a calculator with 3 in place of x.
    I wouldnt advise using a calculator, its best to do by hand as you can simplify in a more natural way. You could use it after for a messy value if you wanted though.
    • Thread Starter
    Offline

    2
    ReputationRep:
    i got(i diddnt us ea cal) .-Sqrt6 +12 sqrt 3 divided by 12 for the function one?
    Offline

    16
    ReputationRep:
    (Original post by FranticMind)
    I wouldnt advise using a calculator, its best to do by hand as you can simplify in a more natural way. You could use it after for a messy value if you wanted though.
    Sorry, I agree with this.


    OP;

    a) i)y+2
    ii) 2^3-x=2^3-log (2)y (2 is a subscript)

    b) Are you sure you have copied a) and b) out correctly? I can't see how to eliminate the log, or why they would write '2^3' not 8.
    Offline

    16
    ReputationRep:
    (Original post by cheesecake11)
    i got(i diddnt us ea cal) .-Sqrt6 +12 sqrt 3 divided by 12 for the function one?
    I got sqrt(3)-8/sqrt(3), so -(5*sqrt(3))/3
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by Octohedral)
    I got sqrt(3)-8/sqrt(3), so -(5*sqrt(3))/3
    oh? i guess i willl jst have to ask for an extention,i dont like rushing with maths!! arggh stupid illness! i 'll learn the logs thing and the function notation today and try again.thanks anyhow
    Offline

    21
    ReputationRep:
    (Original post by cheesecake11)
    oh? i guess i willl jst have to ask for an extention,i dont like rushing with maths!! arggh stupid illness! i 'll learn the logs thing and the function notation today and try again.thanks anyhow
    None of this requires logs as most log work uses a calculator and doesn't appear until C2

    this should be a simple manipulation of laws of indices

    a^m x a^n = a^(m + n)
    a^m / a^n = a^(m - n)

    if y=3^n

    so 3^(3 + n) = 3^3 x 3^n = 27 x 3^n = 27y

    and 3^(2 - n) = 3^2 / 3^n = 9/y

    3 tips
    Show what working you have done so people can help you solve your misunderstandings
    Ask for help more than 20 mins before work should be in - most people who can help will be in lessons at 11:42 (either teaching or learning)
    Post maths probs in the maths forum: http://www.thestudentroom.co.uk/forumdisplay.php?f=38
 
 
 

University open days

  • Heriot-Watt University
    School of Textiles and Design Undergraduate
    Fri, 16 Nov '18
  • University of Roehampton
    All departments Undergraduate
    Sat, 17 Nov '18
  • Edge Hill University
    Faculty of Health and Social Care Undergraduate
    Sat, 17 Nov '18
Poll
Black Friday: Yay or Nay?
Help with your A-levels

All the essentials

The adventure begins mug

Student life: what to expect

What it's really like going to uni

Rosette

Essay expert

Learn to write like a pro with our ultimate essay guide.

Uni match

Uni match

Our tool will help you find the perfect course for you

Study planner

Create a study plan

Get your head around what you need to do and when with the study planner tool.

Study planner

Resources by subject

Everything from mind maps to class notes.

Hands typing

Degrees without fees

Discover more about degree-level apprenticeships.

A student doing homework

Study tips from A* students

Students who got top grades in their A-levels share their secrets

Study help links and info

Can you help? Study help unanswered threadsRules and posting guidelines

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.