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受欢迎的函数 >

extreme f(x)=-7x^3+21x+5

解答

极值点

f (x) = - 7 x^{3} + 21 x + 5

解答

极小值 (- 1, - 9), 极大值 (1, 19)

求解步骤

f^{'} (x) = - 21 x^{2} + 21

Find intervals:

递减

: - \infty < x < - 1,

递增

: - 1 < x < 1,

递减

: 1 < x < \infty

将

x = - 1

代入

- 7 x^{3} + 21 x + 5 : - 9

极小值 (- 1, - 9)

将

x = 1

代入

- 7 x^{3} + 21 x + 5 : 19

极大值 (1, 19)

极小值 (- 1, - 9), 极大值 (1, 19)

作图

流行的例子

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