微积分I(标准路径) · 免费预览

§3.4 Using derivatives to describe families of functions (continued)

给定一个依赖于一个或多个参数的函数族,该函数族中典型函数的图象形状如何依赖于参数的取值?

1. Summary

Summary

2. Cubic family with a repeated root

For p(x)=x3−ax2p(x) = x^3 - ax^2 with a>0a \gt 0, the derivative factors as p′(x)=x(3x−2a)p'(x) = x(3x - 2a) and p′′(x)=6x−2ap''(x) = 6x - 2a. The critical numbers and inflection point are

3. Pole versus hole at the denominator zero

For q(x)=e−xx−cq(x) = \frac{e^{-x}}{x - c}, the function has a vertical asymptote at x=cx = c because

4. Pole versus hole at the denominator zero

For q(x)=e−xx−cq(x) = \frac{e^{-x}}{x - c}, the function has a vertical asymptote at x=cx = c because the denominator vanishes there while the numerator equals e−c≠0e^{-c} \ne 0.

5. Critical number of the pole family

For the same family, the derivative simplifies to q′(x)=−x−c+1(x−c)2exq'(x) = -\frac{x - c + 1}{(x-c)^2e^x}. The only critical number and its location relative to the pole are

6. Bell curve critical point

For the bell shaped family E(x)=e−(x−m)22s2E(x) = e^{-\frac{(x-m)^2}{2s^2}} with s>0s \gt 0, the unique critical number is

7. Inflection points of the bell curve

For the same family E(x)=e−(x−m)22s2E(x) = e^{-\frac{(x-m)^2}{2s^2}}, the inflection points occur at

8. Bell curve tails

For the same family, the limits lim⁡x→∞E(x)\lim_{x \to \infty}E(x) and lim⁡x→−∞E(x)\lim_{x \to -\infty}E(x) are

9. Derivative at the bell center

For E(x)=e−(x−m)22s2E(x) = e^{-\frac{(x-m)^2}{2s^2}}, compute E′(m)E'(m).

10. Cubic family critical number with a value

For the family p(x)=x3−ax2p(x) = x^3 - ax^2 with a=6a = 6, one critical number is x=0x = 0. Compute the other one.

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