Determine f'(x) for the following functions: a) f(x) = (x + 5)^2 b) f(x) = (2x - 3)^2 c) f(x) = (x - 1)^3

Understand the Problem
The question asks us to determine the derivative, denoted as f'(x), for three different functions: f(x) = (x+5)^2, f(x) = (2x-3)^2, and f(x) = (x-1)^3. This involves applying the rules of differentiation, such as the power rule and the chain rule.
Answer
a. $f'(x) = 2x + 10$ b. $f'(x) = 8x - 12$ c. $f'(x) = 3x^2 - 6x + 3$
Answer for screen readers
a. $f'(x) = 2x + 10$ b. $f'(x) = 8x - 12$ c. $f'(x) = 3x^2 - 6x + 3$
Steps to Solve
- Differentiate $f(x) = (x + 5)^2$
Apply the power rule and chain rule. The power rule states that if $f(x) = x^n$, then $f'(x) = nx^{n-1}$. The chain rule states that if $f(x) = g(h(x))$, then $f'(x) = g'(h(x)) \cdot h'(x)$.
So, $f'(x) = 2(x+5)^{2-1} \cdot \frac{d}{dx}(x+5) = 2(x+5)(1) = 2x + 10$.
$$f'(x) = 2(x+5)$$ $$f'(x) = 2x + 10$$
- Differentiate $f(x) = (2x - 3)^2$
Again, use the power rule and the chain rule.
$f'(x) = 2(2x-3)^{2-1} \cdot \frac{d}{dx}(2x-3) = 2(2x-3)(2) = 4(2x-3) = 8x - 12$.
$$f'(x) = 2(2x - 3) \cdot 2$$ $$f'(x) = 4(2x - 3)$$ $$f'(x) = 8x - 12$$
- Differentiate $f(x) = (x - 1)^3$
Apply the power rule and chain rule one more time.
$f'(x) = 3(x-1)^{3-1} \cdot \frac{d}{dx}(x-1) = 3(x-1)^2(1) = 3(x-1)^2$.
$$f'(x) = 3(x-1)^2$$ $$f'(x) = 3(x^2 - 2x + 1)$$ $$f'(x) = 3x^2 - 6x + 3$$
a. $f'(x) = 2x + 10$ b. $f'(x) = 8x - 12$ c. $f'(x) = 3x^2 - 6x + 3$
More Information
The derivative of a function represents its instantaneous rate of change at any given point. It's a fundamental concept in calculus and is used across various fields like physics, engineering, and economics.
Tips
A common mistake is forgetting to apply the chain rule, especially when differentiating composite functions. Another mistake is incorrectly applying the power rule. For example, in part a, some might forget to multiply by the derivative of $(x+5)$ which is 1. While it doesn't change the answer in this case, neglecting it in other scenarios will lead to an incorrect answer.
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