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In Exercises 1-4, use the definition \(f^{\prime}(a)=\lim _{h \rightarrow 0} \frac{f(a+h)-f(a)}{h}\) to find the derivative of the given function at the indicated point. $$f(x)=x^{2}+4, a=1$$

Short Answer

Expert verified
The derivative of the function \( f(x) = x^{2} + 4 \) at the point \( a = 1 \) is \( f'(1) = 2(1) = 2 \).

Step by step solution

01

Substitution of the function into the derivative definition

The first step is to replace \(f(a) \) and \(f(a+h)\) with the corresponding expressions from the given equation. Thus, \(f(a) = a^{2} + 4\) and \(f(a+h) = (a+h)^{2} + 4\). Hence, the derivative function \(f'(a)\) becomes: \(f'(a) = \lim_{h \rightarrow 0} \frac{((a+h)^{2} + 4) - (a^{2} + 4)}{h}\).
02

Simplifying the expression in the numerator

Simplify the expression in the numerator by expanding the term \((a+h)^{2}\), and simplifying it with \(a^{2} + 4\), resulting in: \(f'(a) = \lim_{h \rightarrow 0} \frac{2ah + h^{2}}{h}\).
03

Factoring out h in the numerator

This step involves simplifying the numerator by factoring out \(h\), to get \(f'(a) = \lim_{h \rightarrow 0} \frac{h(2a + h)}{h}\).
04

Cancelling h

Cancel the \(h\) in the numerator and denominator. This leaves \(f'(a) = \lim_{h \rightarrow 0} 2a + h.\)
05

Apply the limit

Lastly, apply the limit definition \( \lim_{h \rightarrow 0}\) and let \(h\) tend to zero. The value of \(f'(a)\) hence become: \(f'(a) = 2a\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Limit Process
The limit process is a foundational concept in calculus, especially when calculating derivatives. It represents the idea of approaching a particular value. In the context of finding a derivative, it involves evaluating the expression as it gets infinitely close to a certain point.
For example, let's consider the expression \(\lim_{h \rightarrow 0} \frac{f(a+h)-f(a)}{h}\). The limit helps us find what happens to the expression as \(h\) gets closer and closer to zero.
It allows us to understand how a function changes in an infinitely small interval around the point \(a\).
  • Imagine zooming in on a graph to such an extent that a curve almost becomes a straight slope.
  • The limit captures this exact change in the slope as we narrow down the interval around the point.
Understanding the limit process is essential, as it helps translate the concept of instantaneous rate of change into a mathematical expression.
Differentiation
Differentiation is the process of finding the derivative of a function, which essentially measures how the function changes as its input changes. Using the limit definition \(f'(a)=\lim_{h \rightarrow 0} \frac{f(a+h)-f(a)}{h}\), we derive functions that describe the slope of the tangent line at any point on the curve.
By substituting the function values into the definition, we turn the abstract concept of rate of change into a calculable number.
  • It's like determining how steep a hill is, where a steeper hill corresponds to a larger derivative.
  • Differentiation turns a curve on a graph into its slope at a point, enabling analysis of the function's behavior.
Differentiation is a powerful tool that is widely used in various fields of science and engineering to understand and predict changing systems.
Function Evaluation
Function evaluation is an integral step when applying the derivative formula. It involves plugging specific values into a function to find its output or behavior at specific points.
In this exercise, \(f(a)=a^{2} + 4\) and \(f(a+h)=(a+h)^{2} + 4\) need to be plugged into the derivative formula.
Once the expressions are substituted, it provides numerical terms, making subsequent steps easier to handle.
  • This helps us see exactly how the function behaves around the interest point.
  • It's essential to accurately substitute and simplify functions to avoid calculation errors.
Function evaluation translates abstract formulas into concrete results, essential for accurate problem-solving.
Algebraic Manipulation
Algebraic manipulation involves rearranging and simplifying expressions to make them easier to understand or solve. After substituting in the values during the differentiation process, \(f'(a) = \lim_{h \rightarrow 0} \frac{(a+h)^{2} - a^{2}}{h}\) requires expansion and simplification.
Expand \((a+h)^{2}\) to \(a^2 + 2ah + h^2\), allowing terms \(a^2\) to cancel out with each other.
  • Factoring and cancelling terms helps to lower complexities in expressions like \(\frac{2ah + h^{2}}{h}\).
  • Ensuring precision in each step avoids errors while canceling terms and applying the limit process.
Mastery of algebraic manipulation enables efficient movement through problems, making the calculus process smoother and reducing errors.

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