Q41 of 43 Page 12

(i) 2x - 
(ii) (5x3 + 3x – 1)(x – 1)
(iii) x-3(5 + 3x)
(v) x-4(3 – 4x-5)
(vi) f


(i) Let f(x) = 2x -

f’(x) = =

      = = 2

(ii) Let f(x) = (5x3 + 3x – 1)(x – 1)

f’(x) = (x – 1) + (5x3 + 3x – 1)

      = (x – 1)

      = (x – 1)

      = (x – 1) [5(3x3-1) – 3] + (5x3 + 3x – 1)

      = (x – 1) [15x2 – 3] + (5x3 + 3x – 1)

      = 15x3 – 3x – 15x2 + 3 + 5x2 + 3x – 1

      = 20x3 – 15x2 + 2

(iii) Let f(x) = x-3(5 + 3x)

f’(x) =

      = x-3

       = x-3

     = x-3

     = 3x-3 - (15 – 9x) x-4

     = =

     =

(iv) Let f(x) = x5(3 – 6x-9) = 3x5 – 6x-4

f’(x) =

      = 

      =

      = (3)(5) x4 – (6) (-4) x-5


      = 15x4 + 24x-5

(v) Let f(x) = x-4(3 – 4x-5)

f’(x) = x-4

       = x-4

       = x-4[0 – (4)(-5)x6] + (3 - 4x-5)(-4)x-5

      = x-4[20 x6] – x-5(12 - 16x5)(-4)x-5

      = 20 x-10 – 12x-5 + 16x-10 = 36 x-10 – 12 x-5

(vi) Let f(x) =

f’(x) = = -

      = -

      =

     = -

     = - =

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