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Homework Help: Simultaneous Equations check on work

  1. Nov 22, 2009 #1
    Guys I have an assigment to hand in I am back at college again. Mature student
    so as this might be simple for some it sometimes is not for me(out of school 10 years)
    I have uploaded 3 pages, questions 1,2,3 I have completed. but I just need to have them checked to see if they are correct.

    And then Question 4 I am totally lost on what to do.
    I would be really grateful for any help

    thank you

    1. The problem statement, all variables and given/known data

    (Simultaneus Equations)
    The Sum of the ages of 2 Wind Turbines is 46 months. The Modern Wind turbine
    is 10 months younger than the other. calculate their present ages and confirm your
    answer by graphical means

    3. The attempt at a solution

    2x+y=46 2x being the 2 turbines 46being the number of months


    x+Y=-10 -10 being the turbine 10 months younger.
    1. The problem statement, all variables and given/known data

    Attached Files:

  2. jcsd
  3. Nov 22, 2009 #2


    Staff: Mentor

    Your writing is too small for me to read in the first two files. For the third problem, you are not translating the given information into mathematical symbols correctly in either equation.

    Let x = the age of the older turbine
    Let y = the age of the newer turbine

    "The sum of the ages of the 2 wind turbines is 46 months."
    x + y = 46

    "The modern wind turbine
    is 10 months younger than the other." becomes
    y = x - 10

    These are the equations you need to use.
  4. Nov 22, 2009 #3
    Hi Mark thanks for replying I have uploaded the first 2 documents again, sorry about my writing it's terrible

    Attached Files:

    • 4.jpg
      File size:
      14.4 KB
    • 5.jpg
      File size:
      13 KB
    • 6.jpg
      File size:
      14.5 KB
  5. Nov 22, 2009 #4


    Staff: Mentor

    It would be helpful if you could type in what you have so that we don't have to open an attachment.
    In the first file, 1a is correct, 1b is correct as far as it goes (combine the two middle terms), and 1c has an incorrect term ( (-5)(-2) isn't -10). Also, you should insert = signs between any two expressions that are equal. Your work doesn't show any of them, and it should.

    In the second file, there are actually two solutions; b = +/-sqrt(12k^2 - a^2). It might be that it is physically impossible for b to be negative, but unless you know that, you should show both solutions.

    You didn't mention it, but your third file is different this time from the one posted originally. Parts a, c, and d are fine, and part b is technically correct, but you shouldn't write exponents as mixed numbers. Instead of writing the exponent as -3 2/3, write it as -11/3. Same goes for part c. Don't write the exponent as 1 1/4; write it as 5/4.
  6. Nov 22, 2009 #5

    Hi Mark yeah I was in a rush to write it down again before you went offline.So I made a few mistakes, but my original work is correct from what you say. Question 2 I will work out for both - and + , and also thanks for telling me the correct way to write exponents.
    That has helped me alot thanks very much
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