Math Problem Statement

Given
f ( x )

3 x − 2 , find
f ′ ( 1 ) using the definition of a derivative.

Solution

To find f(1)f'(1) using the definition of a derivative, we use the limit definition of the derivative:

f(a)=limh0f(a+h)f(a)hf'(a) = \lim_{h \to 0} \frac{f(a+h) - f(a)}{h}

In this case, f(x)=3x2f(x) = 3x - 2, and we are asked to find f(1)f'(1). So, we set a=1a = 1 and proceed step by step.

Step 1: Substitute f(x)=3x2f(x) = 3x - 2 and a=1a = 1 into the limit definition:

f(1)=limh0f(1+h)f(1)hf'(1) = \lim_{h \to 0} \frac{f(1+h) - f(1)}{h}

Step 2: Compute f(1+h)f(1+h) and f(1)f(1)

  • f(1+h)=3(1+h)2=3+3h2=1+3hf(1+h) = 3(1+h) - 2 = 3 + 3h - 2 = 1 + 3h
  • f(1)=3(1)2=1f(1) = 3(1) - 2 = 1

Step 3: Substitute these into the limit expression:

f(1)=limh0(1+3h)1hf'(1) = \lim_{h \to 0} \frac{(1 + 3h) - 1}{h}

Step 4: Simplify the expression:

f(1)=limh01+3h1h=limh03hhf'(1) = \lim_{h \to 0} \frac{1 + 3h - 1}{h} = \lim_{h \to 0} \frac{3h}{h}

Step 5: Cancel hh and compute the limit:

f(1)=limh03=3f'(1) = \lim_{h \to 0} 3 = 3

Final Answer:

f(1)=3f'(1) = 3

Would you like more details, or do you have any questions?

Here are 5 related questions:

  1. How would you find f(2)f'(2) using the same method?
  2. What is the geometric meaning of the derivative at x=1x = 1?
  3. How does the derivative of f(x)=3x2f(x) = 3x - 2 compare to the slope of the line?
  4. Can you apply the definition of the derivative to a nonlinear function like f(x)=x2f(x) = x^2?
  5. What happens to the derivative if the function is constant?

Tip: The derivative of a linear function like f(x)=3x2f(x) = 3x - 2 is always the slope of the line, which remains constant for all xx.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivative
Limit Definition of Derivative

Formulas

f'(a) = lim(h -> 0) [(f(a+h) - f(a)) / h]

Theorems

Limit Definition of the Derivative

Suitable Grade Level

Grades 11-12