Math Problem Statement

This question is to emphasize how our differentiation rules can be used even when it doesn't look like you know enough about a function. (This is a handy trick to use when your formula is very long to write out.)

Set h(x)=1+f(x)g(x) , where f and g are differentiable functions that satisfy

f(−3)=6 ,

f′(−3)=4 ,

g(−3)=5 , and

g′(−3)=2 .

Write down a formula for h′(x) on paper. Using this and the information above, find the value of h′(−3) . Answer: h′(−3)=

Solution

To find h(x)h'(x) where h(x)=1+f(x)g(x)h(x) = 1 + f(x)g(x), we can use the product rule of differentiation. The product rule states that if h(x)=f(x)g(x)h(x) = f(x)g(x), then h(x)=f(x)g(x)+f(x)g(x)h'(x) = f'(x)g(x) + f(x)g'(x).

Given that h(x)=1+f(x)g(x)h(x) = 1 + f(x)g(x), the constant 1 has a derivative of 0. Therefore, we only need to differentiate f(x)g(x)f(x)g(x).

So, h(x)=ddx[1+f(x)g(x)]=ddx[f(x)g(x)]h'(x) = \frac{d}{dx}[1 + f(x)g(x)] = \frac{d}{dx}[f(x)g(x)].

Applying the product rule, we get: h(x)=f(x)g(x)+f(x)g(x)h'(x) = f'(x)g(x) + f(x)g'(x)

Now, we need to evaluate h(x)h'(x) at x=3x = -3.

Given: f(3)=6f(-3) = 6 f(3)=4f'(-3) = 4 g(3)=5g(-3) = 5 g(3)=2g'(-3) = 2

Substitute these values into the derivative formula: h(3)=f(3)g(3)+f(3)g(3)h'(-3) = f'(-3)g(-3) + f(-3)g'(-3) h(3)=(4)(5)+(6)(2)h'(-3) = (4)(5) + (6)(2) h(3)=20+12h'(-3) = 20 + 12 h(3)=32h'(-3) = 32

Thus, the value of h(3)h'(-3) is 3232.

Answer: h(3)=32h'(-3) = 32

Would you like more details or have any questions about this solution?

Here are 5 related questions for further practice:

  1. If k(x)=2+f(x)g(x)k(x) = 2 + f(x)g(x), how would you find k(3)k'(-3) using the given values of ff and gg and their derivatives?
  2. What is the derivative of h(x)=f(x)g(x)+xh(x) = f(x)g(x) + x at x=3x = -3?
  3. How would the product rule apply if h(x)=f(x)g(x)h(x)h(x) = f(x)g(x) \cdot h(x)?
  4. How can you verify the result of h(3)=32h'(-3) = 32 by using numerical differentiation techniques?
  5. How would you apply the chain rule to differentiate h(x)=f(g(x))h(x) = f(g(x))?

Tip: When differentiating a product of two functions, remember to apply the product rule carefully and substitute the known values at the specific point to find the derivative at that point.

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Math Problem Analysis

Mathematical Concepts

Calculus
Differentiation
Product Rule

Formulas

Product Rule: (fg)' = f'g + fg'
h'(x) = f'(x)g(x) + f(x)g'(x)

Theorems

Product Rule of Differentiation

Suitable Grade Level

Grades 11-12 (Advanced Calculus)