mathematics question :(

• POP222

  18 Dec 11, 13:41

  Hi! Can someone help me solve this question? I have the answer but i dont understand the steps so i need someone to help me with the solutions step by step. The question is:

  Given that (2x – 1)(x + m) = 2x² + nx – 3, find the value of

  a) m

  b) n

   

  I really need someone to help me asap! thank you.

• wee_ws

  18 Dec 11, 13:50

  Hi,

    1. Expand the LHS expression.

    2. To find m, compare the constants in the LHS and RHS expressions.

    3. To find n, compare the coefficients of x in the LHS and RHS expressions.

    Thanks.

  Cheers,
  Wen Shih

• POP222

  18 Dec 11, 14:16

  sorry but how do you compare the constants and coefficients? i dont really get the second and third step. 

   

• wee_ws

  18 Dec 11, 14:47

  Hi,

    Let's say x^2 - px + 7 = x^2 + 4x - q, we will then conclude that

    1. -p = 4 by comparing the coefficients of x on both sides,

    2. -q = 7 by comparing the constants on both sides.

    Thanks.

  Cheers,
  Wen Shih

• POP222

  18 Dec 11, 15:10

  can you explain the meaning of coefficient and constants? 

  and do you know what topic is this question under?

   

• eagle

  18 Dec 11, 15:15

  ax^2 + bx + c

   

  a  is a coefficient of x^2

  b  is a coefficient of x

  c  is a constant

   

  This is probably under the topic of quadratic equations?

• POP222

  18 Dec 11, 15:41

  then for my question, how do i find the value of n? I  dont know how to get the asnwer for that question still.

• wee_ws

  18 Dec 11, 19:49

  Hi,

    To find n, you will need the value of m. Thanks.

  Cheers,
  Wen Shih

• eagle

  19 Dec 11, 00:26

  Hi POP, 

  I hope you understand that we are trying to guide you instead of spoonfeeding the answer.

  It's the hols and I assure you that you will improve greatly if you can figure it the answer out with our hints. Keep the questions coming :)

• wee_ws

  19 Dec 11, 08:35

  Hi,

    By step 1, we obtain

    LHS = 2X^2 + 2mx -x - m = 2x^2 + x(2m - 1) - m.

    By step 2, we obtain

    -m = -3, so m = 3.

    By step 3, we obtain

    2m - 1 = n, so with m = 3, we have

    n = 2(3) - 1 = 5.

    Hope these make clear the relationship between our hints and the exact working details.

    Here is another question for you to practise:

    If (2x - m)(x + 3) = 2x^2 + 5x + n, find the values of m and n.

    Jiayou and keep trying!

  Cheers,
  Wen Shih

• 16/f/lonely

  19 Dec 11, 16:03

  Can one use the Gaussian Elimination method here?

• wee_ws

  19 Dec 11, 18:39

  Hi,

    The method is suited to matrices.

  Cheers,
  Wen Shih