Math Problem Statement

Soit la fonction f définie par f(x) = (-6x - 4)e^(9x - 8). Déterminer la dérivée de f.

Solution

The given function is:

f(x)=(6x4)e9x8f(x) = (-6x - 4)e^{9x - 8}

We are tasked with finding its derivative. To compute this, we will apply the product rule, as f(x)f(x) is the product of two functions:

  • u(x)=6x4u(x) = -6x - 4
  • v(x)=e9x8v(x) = e^{9x - 8}.

The product rule states:

f(x)=u(x)v(x)+u(x)v(x).f'(x) = u'(x)v(x) + u(x)v'(x).

Step 1: Compute u(x)u'(x) and v(x)v'(x)

  • u(x)=6x4    u(x)=6u(x) = -6x - 4 \implies u'(x) = -6,
  • v(x)=e9x8    v(x)=9e9x8v(x) = e^{9x - 8} \implies v'(x) = 9e^{9x - 8} (using the chain rule).

Step 2: Apply the product rule

Now substitute into the product rule:

f(x)=(6)(e9x8)+(6x4)(9e9x8).f'(x) = (-6)(e^{9x - 8}) + (-6x - 4)(9e^{9x - 8}).

Step 3: Simplify

Factor out e9x8e^{9x - 8}:

f(x)=e9x8[6+9(6x4)].f'(x) = e^{9x - 8} \big[ -6 + 9(-6x - 4) \big].

Simplify the terms inside the brackets:

6+9(6x4)=654x36=54x42.-6 + 9(-6x - 4) = -6 - 54x - 36 = -54x - 42.

Thus, the derivative is:

f(x)=e9x8(54x42).f'(x) = e^{9x - 8}(-54x - 42).

Or equivalently:

f(x)=e9x8(54x+42).f'(x) = -e^{9x - 8}(54x + 42).

Let me know if you'd like further clarification or additional details on this solution!


Relative Questions:

  1. How can the product rule be applied to other composite functions?
  2. What is the importance of the chain rule when differentiating exponential functions?
  3. How does factoring simplify derivative expressions in general?
  4. Can the derivative f(x)f'(x) be further simplified for specific values of xx?
  5. How would the derivative change if the exponential's base were not ee?

Tip:

Always double-check intermediate steps when applying the product or chain rules to ensure accuracy in computations!

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Math Problem Analysis

Mathematical Concepts

Differentiation
Product Rule
Chain Rule
Exponential Functions

Formulas

f'(x) = u'(x)v(x) + u(x)v'(x)
Derivative of e^(ax+b) = ae^(ax+b)

Theorems

Product Rule for Derivatives
Chain Rule

Suitable Grade Level

Grades 11-12 (Advanced High School or College Calculus)