Math Problem Statement

If f(x) = -5x^2 + 3x, which of the following determines the derivative of f(x)?

Solution

To find which option determines the derivative of f(x)=5x2+3xf(x) = -5x^2 + 3x, we need to apply the definition of the derivative using the limit process:

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

Step-by-Step Process:

  1. Find f(x+h)f(x+h): f(x+h)=5(x+h)2+3(x+h)f(x+h) = -5(x+h)^2 + 3(x+h) Expanding: f(x+h)=5(x2+2xh+h2)+3(x+h)f(x+h) = -5(x^2 + 2xh + h^2) + 3(x+h) =5x210xh5h2+3x+3h= -5x^2 - 10xh - 5h^2 + 3x + 3h

  2. Subtract f(x)f(x) from f(x+h)f(x+h): f(x+h)f(x)=(5x210xh5h2+3x+3h)(5x2+3x)f(x+h) - f(x) = (-5x^2 - 10xh - 5h^2 + 3x + 3h) - (-5x^2 + 3x) Simplifying: =10xh5h2+3h= -10xh - 5h^2 + 3h

  3. Divide by hh: f(x+h)f(x)h=10xh5h2+3hh\frac{f(x+h) - f(x)}{h} = \frac{-10xh - 5h^2 + 3h}{h} Simplifying further: =10x5h+3= -10x - 5h + 3

  4. Take the limit as h0h \to 0: limh0(10x5h+3)=10x+3\lim_{h \to 0} (-10x - 5h + 3) = -10x + 3

Thus, the derivative of f(x)f(x) is f(x)=10x+3f'(x) = -10x + 3.

Now, match this process to the options provided in the image:

The correct expression is the one that applies the definition of the derivative: 5(x+h)2+3(x+h)(5x2+3x)h\frac{-5(x+h)^2 + 3(x+h) - (-5x^2 + 3x)}{h} This matches Option 2.

Let me know if you'd like more details or have any questions!

Related Questions:

  1. What is the definition of a derivative and how is it applied?
  2. How do you expand binomials like (x+h)2(x+h)^2?
  3. What is the geometric interpretation of the derivative?
  4. How would the derivative change if the function were cubic instead of quadratic?
  5. Why do we take the limit as h0h \to 0 in the derivative definition?

Tip:

Always simplify the function f(x+h)f(x)f(x+h) - f(x) carefully before dividing by hh and taking the limit.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Limits

Formulas

Derivative definition: f'(x) = lim (h->0) [(f(x+h) - f(x))/h]

Theorems

Limit definition of a derivative

Suitable Grade Level

College Level (Calculus 1)