Determine the maximum value of y = 3x- x

  • A zero
  • B 2
  • C 4
  • D 6
jamb 2003mathematics

The correct answer is C. 4

y = 3x

- x

dy/dx = 6x - 3x

as dy/dx = 0

6x - 3x

= 0

3x (2 - x) = 0

this implies that 2 -x = 0 and 3x = 0

x = 2 (or) 0

But = dy/dx = 6x - 3x

d

y/dx

= 6 - 6x at x = 2

= 6 - 6(2)

= -6

y = 3x

- x

= 3(2)

- 2

= 12 - 8

= 4

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