数学题英文版跟二阶导有关 The curve y = ax^3 + bx^2 − x + 5 has a poin_数学解答

数学题英文版跟二阶导有关 The curve y = ax^3 + bx^2 − x + 5 has a point of inflexion
The curve y = ax^3 + bx^2 − x + 5 has a point of inflexion at (1, −2). Find the values of a and b.

人气：460 ℃　时间：2020-05-11 21:56:24

解答

点(1,−2).在曲线上,代入可得：-2=a+b+4两价导数为：y''=6aX+2b两价导数为零时是曲线拐点：代入得:6a+2b=0解方程组-2=a+b+46a+2b=0得：a=3,b=-9即y= 3x^3 - 9x^2 − x + 5 验证：3* 1^3 - 9*1^2 − 1...