Wednesday, 2 July 2014

Homework: Study Notes (p30) Discussion 1

How would you determine if the points A (2, -5) and B (5, 2) lie on the straight line y = 3x - 5?

Key in your responses in "Comments".
Remember to enter your group number.

39 comments:

  1. If A (2, -5) lie on y=3x-5,
    -5=3(2)-5
    =6-5
    =1

    Therefore, they do not lie on the straight line y=3x-5

    ReplyDelete
    Replies
    1. Good. So how would you describe your approach in words?

      Delete
    2. substitute x and y into the equation, and since it comes out as -5=1, it does not lie on the line

      Delete
  2. substitute the x and y value of the different points into the equation

    ReplyDelete
    Replies
    1. You are on the right track, but the description is incomplete.
      What would you do after substituting the values?

      Delete
  3. Replies
    1. This is a good suggestion when you do daily practices.
      How would you use graphed?
      Describe.

      Delete
  4. It is not on the line. We can find this out because they give us the formula, we can just substitute the points (X or Y) in the formula to find out the co-ordinates. Group 3

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    Replies
    1. Which formula are you referring to?
      Elaborate.

      Delete
  5. 1) Calculate equation in similar method to Q3 on page 29
    2) Draw out a graph
    3) I still think gradient works but may not be the fastest method
    Grp4

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  6. First find out the gradient of the two points to see if it is 3 because in y=3x-5, 3 is the gradient.
    After calculation we find out that the gradient is 1, which is not the same.
    Therefore the two points do not lie on the straight line y=3x-5.

    ReplyDelete
    Replies
    1. Ria, read the question again.
      Is the question asking us to compare the line formed by the given points or it's just asking us to check if the points A and B lie on the straight line?

      Delete
  7. The gradient of y = 3x - 5 is 3. The gradient of the points A (2, -5) and B (5, 2) has a gradient of 2 1/3.
    We can draw the graph on grapher or the actual graph.
    We can use the formula y=mx+c, for points A (2, -5) and B (5, 2), it is y= 2 1/3x - 9 2/3 and not y=3x-5

    Group 3

    ReplyDelete
    Replies
    1. Prateek, read the question again.
      Is the question asking us to compare the line formed by the given points or it's just asking us to check if the points A and B lie on the straight line?

      So, if you have clarity of the question, what would you do if you are using grapher?
      Alternatively, without the use of Grapher, what would you do? (i.e. under assessment condition)

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  8. By finding out the gradient or substituting x and y values into the equation.
    Group 3.

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    Replies
    1. Nishtha, read the question again.
      Is the question asking us to compare the line formed by the given points or it's just asking us to check if the points A and B lie on the straight line?

      Delete
  9. I still standing on gradient. I don't see any methods honestly.
    So standard finding gradient of 2 points y1-y2/x1-x2 which will give 2+1/3
    If equation is y=3x -5,
    3 --> gradient
    Since gradient is different, they cannot be possible on the same line
    Group 4 :P

    ReplyDelete
    Replies
    1. Yew Chong,
      If we are comparing lines, yes, gradient would be helpful.
      Read the question carefully.
      Is the question asking us to compare the LINE formed by the given points or it's just asking us to check if the POINTS A and B lie on the straight line?

      Delete
  10. We can find out if it lies on the given line because the formula is given, so we can just substitute the points in the formula to find out the co-ordinates.
    Kai Heng Group 3

    ReplyDelete
    Replies
    1. You are in the right track; however, which "formula" are you referring to?
      Elaborate.

      Delete
  11. The gradient of the two points gives us 2 1/3, but the gradient in the equation is 3.

    ReplyDelete
    Replies
    1. Wai Yan
      Read the question again.
      Is the question asking us to compare the line formed by the given points or it's just asking us to check if the points A and B lie on the straight line?

      Delete
  12. We can substitute the points in the equation to find out - Group 1

    ReplyDelete
    Replies
    1. Good!
      How would the values you find help to draw the conclusion if the points lie on the line or not?
      Elaborate further.

      Delete
  13. Draw the graph after finding the y-intersect and the x-intersect using the y = 3x - 5. Check if the points A (2, -5) and B (5, 2) lie on the straight line.
    Group 4

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    Replies
    1. Shanice

      This is one method if we are given a graph paper to plot and check the points.
      What happens, if it's under assessment condition when you do not have the time to do it?
      What are some key ideas and understandings you know about the equation of the straight line can help you to determine if the points lie on the line?

      Delete
  14. replace the values with numbers
    group four

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    Replies
    1. You seemed to be on the right track.
      Now, tell us more about what is the "thing" that you are replacing the values.
      Elaborate further.

      Delete
  15. Since it's given the equation of the line, y=3x-5, we could try substituting the X and Y known from the points given, to see if the points lie along the line of that equation.

    Using Point A(2,-5)
    Eg. If y=3x - 5
    y= 3*2-5
    y=1

    Using B(5,2)
    If y=3x-5
    y=3*5-5
    y=10
    Since both don't give us the given Y coordinate, the points don't lie along the line y=3x-5, since it's Y coordinate would be different if its X coordinate remained the same.
    Group 1

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  16. The gradient is different hence the points are not on the line (gp3)

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    Replies
    1. Keith
      Read the question again.
      Is the question asking us to compare the line formed by the given points or it's just asking us to check if the points A and B lie on the straight line?

      Delete