Pregunta
Evhate the sollowine limits (a) \( \lim _{x \rightarrow 2}\left(x^{2}+x\right)\left(3 x^{2}+6\right) \) (b) \( \lim _{x \rightarrow-2} \sqrt{x^{2}+3 x+6} \)
Ask by Wagner Washington. in South Africa
Jan 23,2025
Solución de tutoría real
Respuesta verificada por el tutor
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The limits are:
(a) 108
(b) 2
Solución
Certainly! Let's evaluate each of the given limits step by step.
---
### Problem (a)
\[
\lim_{x \rightarrow 2} \left(x^{2} + x\right)\left(3x^{2} + 6\right)
\]
**Step 1: Direct Substitution**
Since the functions involved are polynomials, they are continuous everywhere. This means we can directly substitute \( x = 2 \) into the expression.
**Step 2: Substitute \( x = 2 \)**
\[
\begin{align*}
\left(2^{2} + 2\right)\left(3 \times 2^{2} + 6\right) &= \left(4 + 2\right)\left(3 \times 4 + 6\right) \\
&= (6)(12 + 6) \\
&= 6 \times 18 \\
&= 108
\end{align*}
\]
**Answer:**
\[
\lim_{x \rightarrow 2} \left(x^{2} + x\right)\left(3x^{2} + 6\right) = 108
\]
---
### Problem (b)
\[
\lim_{x \rightarrow -2} \sqrt{x^{2} + 3x + 6}
\]
**Step 1: Direct Substitution**
First, check if direct substitution is possible by plugging \( x = -2 \) into the expression inside the square root.
\[
x^{2} + 3x + 6 = (-2)^{2} + 3(-2) + 6 = 4 - 6 + 6 = 4
\]
Since the expression inside the square root is 4, which is non-negative, the square root is defined.
**Step 2: Calculate the Square Root**
\[
\sqrt{4} = 2
\]
**Answer:**
\[
\lim_{x \rightarrow -2} \sqrt{x^{2} + 3x + 6} = 2
\]
---
**Summary:**
- **Problem (a)** evaluates to **108**.
- **Problem (b)** evaluates to **2**.
If you have any further questions or need additional explanations, feel free to ask!
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The Deep Dive
To evaluate the limits, let's jump right in! For the first limit, as \( x \) approaches 2, you can substitute \( x = 2 \) directly into the expression: \[ \lim _{x \rightarrow 2}\left(x^{2}+x\right)\left(3 x^{2}+6\right) = (2^2 + 2)(3(2^2) + 6) = (4 + 2)(12 + 6) = 6 \cdot 18 = 108. \] For the second limit, similarly, substitute \( x = -2 \) into the square root: \[ \lim _{x \rightarrow-2} \sqrt{x^{2}+3 x+6} = \sqrt{(-2)^2 + 3(-2) + 6} = \sqrt{4 - 6 + 6} = \sqrt{4} = 2. \] So the limits are \( 108 \) and \( 2 \) respectively!
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