Volume 3: The Calculus of Life

Workbook 22.3: The Quotient Rule

Directives for the Pillar-Builder:

1. Label the High and Low: Top = $u$, Bottom = $v$.
2. Differentiate Individually: Find $u'$ and $v'$.
3. Follow the Mnemonic: Low-D-High ($v \cdot u'$) minus High-D-Low ($u \cdot v'$).
4. Square the Foundation: Put the result over $(v)^2$.

Part I: Basic Burdens

Find the derivative ($f'$) using the Quotient Rule. Show all parts ($u, v, u', v'$).

$f(x) = \frac{x^2}{x + 3}$

$u = x^2 \implies u' = 2x$
$v = x + 3 \implies v' = 1$
$f'(x) = \frac{(x + 3)(2x) - (x^2)(1)}{(x + 3)^2} = ...$

$f(x) = \frac{5x}{x^2 + 1}$

...

$f(x) = \frac{x^3}{x^2 - 4}$

...
The Logic Check:

Why do we use a Minus Sign in the Quotient Rule, but a Plus Sign in the Product Rule? What does this tell you about the difference between "multiplying" a relationship and "dividing" a responsibility?

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Part II: Multi-Term Burdens

$f(x) = \frac{x^2 + 4x + 1}{2x - 5}$

...

$f(x) = \frac{\sqrt{x}}{x + 10}$

Hint: $u = x^{1/2}$...

Part III: The Challenge (The Efficiency of Koinonia)

The Peace Ratio

A city's "Order" ($O$) is defined as its **Knowledge** ($K$) divided by its **Confusion** ($C$).
$K(t) = 10t^2$ (Knowledge growing over time).
$C(t) = 2t + 5$ (Confusion also growing as the city gets bigger).
Total Order $O(t) = K(t) / C(t)$.

Task: Find the rate of change of Order ($O'$) at $t = 5$ years.

Step 1: Find $K'(t)$ and $C'(t)$...
Step 2: Apply Quotient Rule...
Step 3: Plug in $t=5$...
Is the Order getting better or worse?

Part IV: Transmission (The Echad Extension)

Teacher Log: The Shared Weight

Objective: Explain the Quotient Rule to a younger student using a piggyback ride.

The Activity:
1. Have an older student carry a younger student.
2. Have the younger student "reach up" for a toy (change in $u$).
3. Have the older student "stumble" (change in $v$).

The Lesson: "In a team where one carries another, when the bottom person stumbles, it hurts the whole team. But when the bottom person stays strong (squared), the top person can reach higher!"


Response: ___________________________________________________________

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