a)-What is fof g ofh 3)? fari= gal= bprove f:R¬R fer )=4lis not Surgective and is not injective.

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
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**Mathematics Practice Problems**

**a) Problem:**
Calculate the value of \( f(g(h(3))) \).

Given functions:
- \( f(x) = 2^x \)
- \( g(x) = x^2 \)
- \( h(x) = \frac{x}{4} \)

**b) Problem:**
Prove that the function \( f: \mathbb{R} \rightarrow \mathbb{R} \) defined by \( f(x) = |x| \) is not surjective and is not injective.

---

**Solutions:**

**a) Solution:**

1. **Find \( h(3) \):**
   \[
   h(3) = \frac{3}{4}
   \]

2. **Find \( g(h(3)) \):**
   \[
   g\left(\frac{3}{4}\right) = \left(\frac{3}{4}\right)^2 = \frac{9}{16}
   \]

3. **Find \( f(g(h(3))) \):**
   \[
   f\left(\frac{9}{16}\right) = 2^{\frac{9}{16}}
   \]

**b) Solution:**

*To prove \( f: \mathbb{R} \to \mathbb{R} \), \( f(x) = |x| \) is not surjective:*

- A function is surjective if for every \( y \) in the codomain, there is an \( x \) in the domain such that \( f(x) = y \).
- The codomain is \(\mathbb{R}\), but \( f(x) = |x| \) only outputs non-negative values. Therefore, negative numbers in \(\mathbb{R}\) have no pre-image under \( f \). 
- Thus, \( f \) is not surjective.

*To prove \( f: \mathbb{R} \to \mathbb{R} \), \( f(x) = |x| \) is not injective:*

- A function is injective if \( f(x_1) = f(x_2) \) implies \( x_1 = x_2 \).
- For instance, \( f(1) = 1 \) and \( f(-1) = 1 \), so
Transcribed Image Text:**Mathematics Practice Problems** **a) Problem:** Calculate the value of \( f(g(h(3))) \). Given functions: - \( f(x) = 2^x \) - \( g(x) = x^2 \) - \( h(x) = \frac{x}{4} \) **b) Problem:** Prove that the function \( f: \mathbb{R} \rightarrow \mathbb{R} \) defined by \( f(x) = |x| \) is not surjective and is not injective. --- **Solutions:** **a) Solution:** 1. **Find \( h(3) \):** \[ h(3) = \frac{3}{4} \] 2. **Find \( g(h(3)) \):** \[ g\left(\frac{3}{4}\right) = \left(\frac{3}{4}\right)^2 = \frac{9}{16} \] 3. **Find \( f(g(h(3))) \):** \[ f\left(\frac{9}{16}\right) = 2^{\frac{9}{16}} \] **b) Solution:** *To prove \( f: \mathbb{R} \to \mathbb{R} \), \( f(x) = |x| \) is not surjective:* - A function is surjective if for every \( y \) in the codomain, there is an \( x \) in the domain such that \( f(x) = y \). - The codomain is \(\mathbb{R}\), but \( f(x) = |x| \) only outputs non-negative values. Therefore, negative numbers in \(\mathbb{R}\) have no pre-image under \( f \). - Thus, \( f \) is not surjective. *To prove \( f: \mathbb{R} \to \mathbb{R} \), \( f(x) = |x| \) is not injective:* - A function is injective if \( f(x_1) = f(x_2) \) implies \( x_1 = x_2 \). - For instance, \( f(1) = 1 \) and \( f(-1) = 1 \), so
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