Find the critical points of the function y = 2x ^ 3-6x.
July 25, 2021 | education
| y = 2x ^ 3 – 6x.
Find the derivative of the function:
y ‘= (2x ^ 3 – 6x)’ = 2 * 3x ^ 2 – 6 = 6x ^ 2 – 6.
Critical points are the points at which the derivative is zero:
y ‘= 0,
6x ^ 2 – 6 = 0,
6 (x ^ 2 – 1) = 0,
6 (x – 1) (x + 1) = 0,
x1 = -1,
x2 = 1.
When x <-1, y ‘(x)> 0, then the function is increasing.
When -1 <x <1, y ‘(x) <0, then the function is decreasing.
For x> 1, y ‘(x)> 0, then the function is increasing.
Point x = -1 is the maximum point, y (-1) = 2 * (-1) ^ 3 – 6 * (-1) = -2 + 6 = 4.
Point x = 1 is the minimum point, y (1) = 2 * 1 ^ 3 – 6 * 1 = 2 – 6 = -4.
Critical points: (-1; 4) and (1; -4).
Answer: (-1; 4) and (1; -4).
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