Friday, April 10, 2009

Find dy/dx

1. y = 6x^3 + 4x^2 - 5x

2. y^2 = x^3 + 16

3. 1/y = 4x + 4

4. y = 3x^4 + 3(x^2 + 5)

5. y + 6 = 4x + 9y - 3x^2

41 comments:

  1. ques 1

    as we can see that its many terms, now the easist way to work this ques will be too Differentiate them separately

    1.first you make sure there is no bracket terms
    2.then make sure that there are no downstairs
    3. then you look out for the police

    its as simple as that

    answer y = 18x^2 + 8x - 5

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  2. Question`1

    y=ax^n
    dy/dx=(a)(n)x^n-1

    so

    y = 6x^3 + 4x^2 - 5x
    y`=`(6)(3)x^3-1`+`(4)(2)x^2-1`-`5x
    y`=`18x^2`+`8x`-`5x

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  3. quest 1

    first you look to see which one of the rules you are dealing with then you proceed.

    so clearly this one is dealing with ax^n
    so dy/dx = anx^n-1

    so the ans. = 18x^2 + 8x - 5

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  4. Question 1

    this Question deals with ax^n
    therefore dy/dx = anx^n-1
    so
    y = 6x^3 + 4x^2 - 5x
    y`=`(6)(3)x^3-1`+`(4)(2)x^2-1`-`5x
    y`=`18x^2`+`8x`-`5x

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  5. 4. y = 3x^4 + 3(x^2 + 5)
    expand the brackets..
    y= 3x^4 + 3x^2 + 15
    then find dy/dx
    so dy/dx= 12x^3 + 6x

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  6. QUES 2

    since i believe that the Differenal of two trems is not on the course map i would figure that u wud just have to make y the subject then Differentiate

    y^2 = x^3 + 16
    y = (x^3 + 16)^0.5

    and well from here its simple jus follow the rules that miss gave us in class and u should be fine

    answer: dy/dx = -1.5x^2(x^3 + 18)^-0.5



    OR

    you can Differentiate the y trem as well in this case you shall get

    dy/dx = 2y dy/dx = 3x^2

    then i believe u make dy/dx subject of the formula


    dy/dx = 3x^2 - 2y

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  7. renjisa n if it's y^2 won't it be difficult to divided by 2.
    won't it be (x^3+16)^-2?

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  8. QUESTION1
    y=6x^3 + 4x^2 -5x
    y=18x^3-1 + 8x^2-1 -5
    y=18x^2+8x-5

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  9. for 2) jus square the other side trid to get rid of y^2..

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  10. 3) to remove the 1/y u carry across the 4x+4

    so itl be 1/4x +4 = y

    which is d same as (4x +4)^ -1 = y

    from there you diff as normal

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  11. y = 3x^4 + 3(x^2 + 5)

    remove brackets

    y= 3x^4 + 3x^2 + 15



    dy/dx= 12x^3 + 6x

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  12. 5. y + 6 = 4x + 9y - 3x^2

    y -9y = 4x - 3x^2 - 6

    y(-9y) =4x - 3x^2 -6

    -9y^2 =4x - 3x^2 -6

    y^2 = 4x - 3x^2 - 6/ -9

    dy/dx= (4 - 6x)^9

    dont forget u hav to square it after to get y alone...

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  13. question4
    y=3x^4+3(x^2+5)
    y=3x^4+3x^2+15
    dy/dx=12x^3+6x

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  14. question5
    y+6=4x+9y-3x^2
    y=4x+9y-3x^2-6
    y=-3x^2+4x+9y-6
    y-9y=-3x^2+4x-6
    -8y=-3x^2+4x-6
    8y=3x^2-4x+6
    y=3/8x^2-4/8x+6/8
    y=6/8x-4/8

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  15. 1. y = 6x^3 + 4x^2 - 5x

    so you say dy/dx = 18 x ^2 + 8x -5x

    you multiply by the power and the minus one form the power

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  16. ok animechic to get rid of a squared term we find the squared root and once you do it too one side of the equ you do to the next side..

    and another way to wirte square root is a value to the power of ah half

    e.g (4x + 3)^0.5 0.5 is the same as 1/2

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  17. POINTS TO NOT PPL

    the heading says find dy/dx right so that means it is with respect to y.


    so all u ahve to do is make y the subject of the formula for all the ques in each case and then just Differenate


    does anyone still dont understand ????

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  18. Question 1.
    y = 6x^3 + 4x^2 - 5x
    dy/dx = 18x^2 + 8x - 5

    Question 2.
    y^2 = x^3 + 16
    I need help with this question

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  19. Question 5
    y + 6 = 4x + 9y - 3x^2

    y = 4x + 9y - 3x^2 - 6

    y - 9y = 4x - 3x^2 - 6

    -8y = 4x - 3x^2 - 6

    y = ( 4x - 3x^2 -6 )/ 6

    Now its just a matter of differentiating

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  20. so question like these you have to make y subject of the formula and then differentiate normal after.

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  21. 1. y = 6x^3 + 4x^2 - 5x
    dy/dx = 18x^2 + 8x - 5

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  22. 2. y^2 = x^3 + 16
    dy/dx= 3x^2
    16 is jus a number dats stands alone hence d differential of it is 0

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  23. Question 5.
    y + 6 = 4x + 9y - 3x^2
    all y variable grouped &
    all x variable grouped
    so
    y -9y = 4x - 3x^2 - 6
    y(-9y) =4x - 3x^2 -6
    -9y^2 =4x - 3x^2 -6
    y^2 = 4x - 3x^2 - 6/ -9
    dy/dx= (4 - 6x)^9

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  24. Question 4.
    y = 3x^4 + 3(x^2 + 5)
    get rid of the brackets by expanding
    so (3*x^2) + (3*5) = 3x^2 + 15
    the equation will continue....
    y= 3x^4 + 3x^2 + 15
    then find dy/dx
    dy/dx= 12x^3 + 6x

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  25. 1.y=6x^3+4x^2-5x
    dy/dx=18x^2+8x-5

    2.y^2=x^3+16
    dy/dx=2y=3x^2

    3.1/y=4x+4
    dy/dx=y^-1=4x+4
    dy/dx=-1y^-2=4

    4.y=3x^4+3(x^2+5) = 3x^4+3x^2+15
    dx/dy=12x^3+6x

    5.y+6=4x+9y-3x^2
    dy/dx=4+9-6x

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  26. for 5 ,y + 6 = 4x + 9y - 3x^2 , which is the correct way ,just differentiating or grouping terms..............i think the way weezy did it but not really sure?

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  27. in differentiation, the method is to multiply the coeff. of x by the power of x then minus 1 to the power of x:
    y = ax^n
    dy/dx = nax^n-1

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  28. 1) y = 6x^3 + 4x^2 - 5x
    dy/dx = 3(6x)^3-1 + 2(4x)^2-1 - 5
    18x^2 + 8x - 5

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  29. Yes "low rider" always make y (or wat is to be differentiated) the subject of the formula before starting to differentiating the equation. Also another thing to take note of is to make put the equation in its simpliest form before differentiating....

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  30. 1. 6x^3 + 4x^2 - 5x

    dy/dx =18x^2 + 8x - 5

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  31. 4. y = 3x^4 + 3(x^2 + 5)

    Removing brackets:
    y = 3x^4 + 3x^2 + 15

    dy/dx = 12x^3 + 6x

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  32. 5. y + 6 = 4x + 9y - 3x^2
    y = 4x + 9y - 3x^2 - 6
    y - 9y = -3x^2 + 4x - 6
    -8y = -3x^2 + 4x - 6

    Divide both sides by (-8)
    y = -3x^2 + 4x - 6 / -8
    y = -3x^2 +4x + (3/4)

    dy/dx = -6x + 4

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  33. 1. y = 6x^3 + 4x^2 - 5x
    when doing this you multiply the coefficent by the power that value now becomes thr coefficent and 1 is minused from the power the power
    y=18X^2+8X-5

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  34. 2. y^2 = x^3 + 16

    look for brackets or notted terms

    2y=3X^2
    when there is a 3 alone the number is removed

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  35. 5. y + 6 = 4x + 9y - 3x^2
    y (-9y )= 4 - 6X - 6
    9Y^2=-2-6X
    dy/dx=(18/6)^2

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  36. 4. y = 3x^4 + 3(x^2 + 5)
    work out the knotted terms and then do normal differentiation

    y=12X^3+ 3X^2+15
    y=12X^3+6X
    dy/dx=12x^3+6x

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  37. A differentiation question & answer!!!>>>

    If T = (3p + 1)^2/ p ,find dT/dp and the values of p for dT/dp = 0.

    Solution^^

    Here we rewrite the expression as a polynomial first:

    (3p + 1)^2 /p
    Dividing each term in the numerators by p

    9p^2 + 6p + 1 /p
    9p + 6 + 1/p
    9p + 6 + p^-1
    Then dT/dp = 9 + 0 + (-1)p^-2 = 9 -(1 /p^2)

    If dT/dp = 0, then 9 = 1/p^2 and p = +or- 1/3

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  38. this 1 iss another eg also

    Differentiate wrt x

    (2x - 3)^2

    Here we express (2x-3)^2 as a polynomial first by expansion::::>so
    (2x - 3)^2
    4x^2 - 12x + 9
    If y 4x^2 - 12x + 9, then
    dy/dx = 8x - 12x^0 + 0 =
    8x - 12,as x^0=1.

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  39. For all of you who tried to ans #2 you should check back your notes that miss give...
    I think the ans you found were wrong.

    y^2 = x^3 + 16
    the 1st thing 2 do is to make y the subject of the formula:

    y = (x^3 + 16)^0.5
    since if you make y the subject then the other side of the equation has to compensate, therefore, in this case the other side becomes the square root or to the power of 0.5

    now you diff.

    y = (x^3 + 16)^0.5
    This is to hard to diff. so im goin to make it simpler as follows:

    substitute
    m = x^3 + 16
    dm/dx = 3x^2

    rewrite:
    y = m^0.5
    dy/dm = 0.5m^-0.5

    The question asked for dy/dx.
    Therefore:

    dy/dx = dm/dx.dy/dm
    dy/dx = (3x^2) X 0.5(x^3 + 16)

    if im wrong plz correct me...

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  40. #5. y + 6 = 4x + 9y - 3x^2

    Make y the subject.
    y = 4x + 9y + 3x^2 - 6

    now diff. But remember this is partial diff.

    dy/dx = 4 + 9dy/dx - 6x

    this is how you do #5...

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