Chapter 2: Problem 17
, find the indicated limit. In most cases, it will be wise to do some algebra first. $$ \lim _{h \rightarrow 0} \frac{(2+h)^{2}-4}{h} $$
Short Answer
Expert verified
The limit is 4.
Step by step solution
01
Expand the Binomial Expression
Start by expanding the expression \((2+h)^2\). Apply the formula for the square of a binomial: \((a+b)^2 = a^2 + 2ab + b^2\). In this case, \((2+h)^2 = 4 + 4h + h^2\).
02
Simplify the Numerator
Substitute the expanded form of \((2+h)^2\) into the numerator of the fraction: \(4 + 4h + h^2 - 4\). Simplify this to get \(4h + h^2\).
03
Write the Simplified Limit Expression
Replace the original expression inside the limit with the simplified form: \(\lim_{h \to 0} \frac{4h + h^2}{h}\).
04
Factor and Simplify
Factor \(h\) out of the numerator: \(\frac{h(4 + h)}{h}\). Cancel \(h\) from the numerator and the denominator to get \(4 + h\).
05
Evaluate the Limit
Finally, evaluate the limit by substituting \(h = 0\) into the simplified expression: \(\lim_{h \to 0} (4 + h) = 4\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Binomial Expansion
Binomial expansion is a process of expanding expressions that are raised to a power. In this case, we have \((2+h)^2\), which follows the binomial theorem. The general formula for the square of a binomial is \((a+b)^2 = a^2 + 2ab + b^2\). This formula allows us to expand \((2+h)^2\) into \(4 + 4h + h^2\).
- \(a = 2\) and \(b = h\)
- \(a^2 = 2^2 = 4\)
- \(2ab = 2 \times 2 \times h = 4h\)
- \(b^2 = h^2\)
Simplifying Expressions
Simplifying expressions means reducing them to their simplest form. Once expanded, \((2+h)^2\) becomes \(4 + 4h + h^2\). Next, incorporate this into the original fraction \(\frac{(2+h)^2 - 4}{h}\).
- Substitute the expanded binomial: \(\frac{4 + 4h + h^2 - 4}{h}\)
- Simplify by subtracting \(4\) from \(4 + 4h + h^2\)
- This reduces the expression to \(4h + h^2\)
Factoring
Factoring involves expressing an expression as the product of its factors. Here, we need to factor the simplified form \(4h + h^2\). Notice both terms share an \(h\). Pull out this common factor:
- Factor \(h\) from \(4h + h^2\): \(h(4 + h)\)
- This gives us the expression \(\frac{h(4 + h)}{h}\)
Evaluating Limits
Evaluating limits is a fundamental concept in calculus, used to find the value that a function approaches as the input approaches some value. With the expression simplified via factoring to \(4 + h\), now it's straightforward to evaluate the limit as \(h\) approaches \(0\).
- Original limit expression: \(\lim_{h \to 0} \frac{4h + h^2}{h}\)
- After simplifying, it becomes \(\lim_{h \to 0} (4 + h)\)
- Substitute \(h = 0\): it results in \(4\)