Chap 2: Real Numbers - Spot the Common Mistakes (II)

Revision Exercise 2 (p52 of Textbook) No. 7(b)



29 comments:

  1. It should not be (-2)^3+(-7)^3 because it is not the same as (-2+(-7))^3

    ReplyDelete
  2. This comment has been removed by the author.

    ReplyDelete
  3. This comment has been removed by the author.

    ReplyDelete
  4. it is not (-2)^3+(-7)^3 because the answer of the sum is not equivalent to (-2+(-7))^3

    ReplyDelete
  5. The working in the Big brackets should be done first. Then it would become (-9)^3=-729

    ReplyDelete
  6. The working should be within the bracket first
    (-9)^3=-729

    ReplyDelete
  7. (-2)^3 + (-7)^3 is not the same as (-9) X (-9) X (-9). The answer should be (-729).

    ReplyDelete
  8. It should be (-9)^3
    =(-9 x -9 x -9)
    =(-729)

    ReplyDelete
  9. it should be [-2-(-7)]^3 and not (-2)^3+(-7)^3 because (-2)^3+(-7)^3 is different from [-2-(-7)]^3

    [-2-(-7)]^3=-729(correct answer)

    (-2)^3+(-7)^3=-351

    ReplyDelete
  10. This comment has been removed by the author.

    ReplyDelete
  11. The correct working should be:
    [-2+(-7)]^3
    =[-2+(-7)]x[-2+(-7)]x[-2+(-7)]
    =(-9)(-9)(-9)
    =81x(-9)
    =(-729)

    ReplyDelete
  12. [-2 + (-7)]^3 is not the same as (-2)^3 + (-7)^3
    in (-2)^3 + (-7)^3, it means multiplying then adding. but the numbers are inside the bracket [-2 + (-7)]^3 and the we should do the working inside the bracket first.
    so the correct working is:
    [-2 + (-7)]^3
    = -9 x (-9) x (-9)
    = -81 x (-9)
    = -729

    ReplyDelete
  13. The person who did this should work out the -2+(-7) first. Then it should be okay and the answer should be (-9)(-9)(-9)= (-729)

    ReplyDelete
  14. =(-2+(-7))x(-2+(-7))x(-2+(-7))
    =(-9)x(-9)x(-9)
    =-729

    ReplyDelete
  15. The working in the bracket should be done first
    [-2-(-7)]^3=-729

    ReplyDelete
  16. The working is wrong.
    Instead of....
    ( -2+(-7) )^3
    =(-2)^3 + (-7)^3
    =-8 + (-393)
    = -351(Ans)

    It should be...
    ( -2+(-7) )^3
    =(-9)^3
    = -729(Ans)

    ReplyDelete
  17. It should be [-2-(-7)]^3 as [-2-(-7)]^3 is different from (-2)^3+(-7)^3

    correct answer:

    [-2+(-7)]^3
    =[-2+(-7)]x[-2+(-7)]x[-2+(-7)]
    =(-9)(-9)(-9)
    =81x(-9)
    =(-729)

    ReplyDelete
  18. The workings in the outer brackets must be done first.After that, take(-9)^3which will give you -729

    ReplyDelete
  19. The answer should be:
    (-2+-7)^3
    =-9^3
    =729

    ReplyDelete
  20. The workings in the first brackets should be solved first. So,(-2+(-7))=-9. (-9)^3= -729

    ReplyDelete
  21. We should work out the (-2+(-7)) first and then (-9)(-9)(-9)so the answer is -729.

    ReplyDelete
  22. It should not be (-2)^3 + (-7)^3 as it is totally different from [-2+(-7)]^3.

    It is (-2+(-7) raised to the power of 3 and not the sum of the individual integers as in (-2+(-7), it is raised to the power of 3 after they are added.

    Therefore, the method is:

    [-2+(-7)]^3
    = (-9)^3
    = -729

    -Christopher Nah

    ReplyDelete
  23. [-2+(-7)]^3
    =[-2=(-7)][-2=(-7)][-2=(-7)]
    =-729

    ReplyDelete
  24. All of you are right! We should do what's in the bracket first since the power 3 is outside the bracket. Some of you explained pretty well :D

    The following presentations needs to be improved on:
    1. Some of you put down answer as (-729).
    If it is the final answer, we should not write the () any more. So, answer should be written as -729

    2. Second line of Darryl's working:
    =[-2=(-7)][-2=(-7)][-2=(-7)]
    Did Darryl typed the sign incorrectly?
    (have to hold shift key)

    3. We should not write
    =(-9 x -9 x -9)
    we cannot park x and - side by side without any ()
    It should therefore be rewritten as
    =(-9) X (-9) X (-9)

    ReplyDelete