Originally Posted by
db5vry A question on my practice exam paper says:
The curve C has equation y = 3x³ - 3x² - 9x + 2. Find the coordinates of the stationary points of C and determine the nature of these points.
I worked part out as:
dy/dx = 3x² - 6x - 9 = 0
(/3) = x² - 2x - 3 = 0
(x-3)(x+1) = 0
x = 3, x = -1
When x=3:
(3)³ - 3(3)² - 9(3) + 2
= 27 - 27 - 27 + 2
= -25
When x=-1:
(-1)³ - 3(-1)² - 9(-1) + 2
= -1 - 3 + 9 + 2
= 7
Coordinates are (3,-25),(-1,7).
Is this right so far and what do I need to do to complete the rest?