Math Problem Statement

Given f(x) = 3x^2 - 5√x, which of the following expressions will represent f'(x)? Also, given f(x) = 2x^2 - 3x and c = 2, find f'(c) using the difference quotient and taking the limit as h approaches 0.

Solution

Let's break down and address each of the two questions based on the image:

1. Derivative using the difference quotient

The first question asks which expression represents f(x)f'(x) for the function:

f(x)=3x25xf(x) = 3x^2 - 5\sqrt{x}

The derivative f(x)f'(x) is defined as the limit:

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

Given the function f(x)=3x25xf(x) = 3x^2 - 5\sqrt{x}, we calculate f(x+h)f(x+h):

f(x+h)=3(x+h)25x+hf(x+h) = 3(x+h)^2 - 5\sqrt{x+h}

Substitute this expression into the difference quotient:

f(x)=limh0(3(x+h)25x+h)(3x25x)hf'(x) = \lim_{h \to 0} \frac{(3(x+h)^2 - 5\sqrt{x+h}) - (3x^2 - 5\sqrt{x})}{h}

The correct expression matching this form from the options provided in the image is:

limh0(3(x+h)25x+h)(3x25x)h\boxed{\lim_{h \to 0} \frac{(3(x+h)^2 - 5\sqrt{x+h}) - (3x^2 - 5\sqrt{x})}{h}}

Thus, the correct answer for this part is the first option.


2. Difference quotient for specific values

The second question involves the function f(x)=2x23xf(x) = 2x^2 - 3x and asks for f(c)f'(c) where c=2c = 2. To do this, we must use the definition of the derivative:

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

Given c=2c = 2, the function becomes f(x)=2x23xf(x) = 2x^2 - 3x. We first calculate f(2)f(2):

f(2)=2(2)23(2)=86=2f(2) = 2(2)^2 - 3(2) = 8 - 6 = 2

Next, we calculate f(2+h)f(2+h):

f(2+h)=2(2+h)23(2+h)f(2+h) = 2(2+h)^2 - 3(2+h) Expanding this:

f(2+h)=2(4+4h+h2)3(2+h)f(2+h) = 2(4 + 4h + h^2) - 3(2+h) f(2+h)=8+8h+2h263hf(2+h) = 8 + 8h + 2h^2 - 6 - 3h f(2+h)=2+5h+2h2f(2+h) = 2 + 5h + 2h^2

Now, use the difference quotient:

f(2)=limh0(2+5h+2h2)2h=limh05h+2h2hf'(2) = \lim_{h \to 0} \frac{(2 + 5h + 2h^2) - 2}{h} = \lim_{h \to 0} \frac{5h + 2h^2}{h} Simplify:

f(2)=limh0(5+2h)=5f'(2) = \lim_{h \to 0} (5 + 2h) = 5

Thus, the answer for f(2)f'(2) is 5\boxed{5}.


Do you have any questions or would you like further details?

Related Questions:

  1. How would you apply the difference quotient for a trigonometric function like sin(x)\sin(x)?
  2. Can you find the second derivative f(x)f''(x) for the function f(x)=3x25xf(x) = 3x^2 - 5\sqrt{x}?
  3. What happens if you calculate the difference quotient for a polynomial function like x3x^3?
  4. How does the chain rule relate to the derivative of 5x5\sqrt{x}?
  5. Can you generalize the difference quotient for functions of multiple variables?

Tip:

Always expand terms carefully when working with the difference quotient to ensure correct simplifications for limits.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivative
Limit
Difference Quotient

Formulas

f'(x) = lim_{h -> 0} [(f(x+h) - f(x)) / h]
f(c) = 2x^2 - 3x
Derivative of a function using the difference quotient

Theorems

Limit definition of the derivative

Suitable Grade Level

Grades 11-12, College-level Calculus