A Maths

• Jasmine ngjiamin

  19 Dec 11, 09:38

  Q 1)  2x² + 5xy + 2y² = 0

           x² - y² = 1 

           find x and y.

  Q 2)  3x + 2y - z = 4

           5x - 7z = 26

           express y in terms of x and y.

• wee_ws

  19 Dec 11, 10:04

  Hi Jasmine,

    Q2 looks problematic when it is to express y in terms of x and y.

    For Q1,

    1. factorise 1st equation;

    2. obtain possible relationships between x and y;

    3. use the relationships in 2nd equation.

    Thanks.

  Cheers,
  Wen Shih

• wee_ws

  19 Dec 11, 11:23

  Hi,

    Q1 (no linear equation) & Q2 (3 unknowns) may not be appropriate as questions in Additional Maths, if we refer to the syllabus statement:

    1.4 Simultaneous equations in two unknowns.
    Include:
    - solving simultaneous equations with at least one linear equation, by substitution;
    - expressing a pair of linear equations in matrix form and solving the equations by inverse matrix method.

    Thanks.

  Cheers,
  Wen Shih

• Jasmine ngjiamin

  19 Dec 11, 13:26

  ok thks^^

• wee_ws

  19 Dec 11, 13:26

  Hi,

    If the original question 1 were to assess higher-order thinking, one may reword it, in Cambridge sense, as follows:

    The real unknowns x and y satisfy the equations

    2x^2 + 5xy + 2y^2 = 0 and x^2 - y^2 = 1.

    (i) By factorising the first equation, find two possible relationships between x and y.

    (ii) Explain why only one relationship is valid and use it to find the possible values of x and y.

    Thanks.

  Cheers,
  Wen Shih

• wee_ws

  19 Dec 11, 13:29

  Hi,

    Q1 can be used as a question in A-level H2 Maths, since complex roots are involved.

    Thanks.

  Cheers,
  Wen Shih