Math Problem Statement

Use the graph of f and g to find the derivatives of the following functions: (a) p'(9) where p(x) = f(x)g(x) and (b) q'(4) where q(x) = f(x)/g(x).

Solution

The problem is asking to find derivatives of two functions:

  1. p(9)p'(9) where p(x)=f(x)g(x)p(x) = f(x)g(x)
  2. q(4)q'(4) where q(x)=f(x)g(x)q(x) = \frac{f(x)}{g(x)}

The graph provided shows both f(x)f(x) and g(x)g(x), so let's use the product and quotient rules for differentiation.

(a) p(9)p'(9) – Product Rule:

For p(x)=f(x)g(x)p(x) = f(x)g(x), the derivative is given by the product rule: p(x)=f(x)g(x)+f(x)g(x)p'(x) = f'(x)g(x) + f(x)g'(x) To calculate p(9)p'(9), we need:

  • f(9)f(9), f(9)f'(9)
  • g(9)g(9), g(9)g'(9)

From the graph at x=9x = 9:

  • f(9)=1f(9) = 1
  • g(9)=4g(9) = 4

Now, the slopes at x=9x = 9 (to find the derivatives):

  • f(9)f'(9): The graph of f(x)f(x) looks flat at x=9x = 9, so f(9)=0f'(9) = 0.
  • g(9)g'(9): From the graph, the slope of g(x)g(x) at x=9x = 9 appears to be 11.

Now substitute into the product rule: p(9)=f(9)g(9)+f(9)g(9)=0×4+1×1=1p'(9) = f'(9)g(9) + f(9)g'(9) = 0 \times 4 + 1 \times 1 = 1

So, p(9)=1p'(9) = 1.

(b) q(4)q'(4) – Quotient Rule:

For q(x)=f(x)g(x)q(x) = \frac{f(x)}{g(x)}, the derivative is given by the quotient rule: q(x)=f(x)g(x)f(x)g(x)g(x)2q'(x) = \frac{f'(x)g(x) - f(x)g'(x)}{g(x)^2} To calculate q(4)q'(4), we need:

  • f(4)f(4), f(4)f'(4)
  • g(4)g(4), g(4)g'(4)

From the graph at x=4x = 4:

  • f(4)=6f(4) = 6
  • g(4)=4g(4) = 4

Now, the slopes at x=4x = 4:

  • f(4)=1f'(4) = -1 (decreasing slope)
  • g(4)=12g'(4) = -\frac{1}{2} (slightly decreasing slope)

Now substitute into the quotient rule: q(4)=f(4)g(4)f(4)g(4)g(4)2=(1)(4)(6)(12)42q'(4) = \frac{f'(4)g(4) - f(4)g'(4)}{g(4)^2} = \frac{(-1)(4) - (6)(-\frac{1}{2})}{4^2} q(4)=4+316=116q'(4) = \frac{-4 + 3}{16} = \frac{-1}{16}

So, q(4)=116q'(4) = -\frac{1}{16}.

Would you like any further details or explanations?


Here are some related questions:

  1. What is the general product rule for differentiation?
  2. How is the quotient rule derived from the product rule?
  3. How do you estimate the slope from a graph visually?
  4. What is the importance of checking points and slopes in real-world contexts?
  5. How can these differentiation techniques be applied in physics or economics?

Tip: Always ensure your slope estimates from graphs are as precise as possible by looking at intervals between points.

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Math Problem Analysis

Mathematical Concepts

Calculus
Differentiation
Product Rule
Quotient Rule

Formulas

Product rule: p'(x) = f'(x)g(x) + f(x)g'(x)
Quotient rule: q'(x) = (f'(x)g(x) - f(x)g'(x)) / (g(x)^2)

Theorems

Product Rule
Quotient Rule

Suitable Grade Level

College Calculus (Calculus I or II)