2.1 Introduction to Part 1 of 3 Evaluate the function \( f(r)=\sqrt{r+4}+3 \) at the given values of the independent variable and simplify. a. \( f(-4) \) b. \( f(12) \) c. \( f(x-4) \) a. \( f(-4)= \) \( \square \) (Simplify your answer.)

Substitute \( r=-4 \) into the expression \( \sqrt{r+4}+3 \). Evaluate the expression by following steps: - step0: Evaluate: \(\sqrt{r+4}+3\) - step1: Substitute: \(\sqrt{-4+4}+3\) - step2: Add the numbers: \(\sqrt{0}+3\) - step3: Simplify the root: \(0+3\) - step4: Remove 0: \(3\) Substitute \( r=12 \) into the expression \( \sqrt{r+4}+3 \). Evaluate the expression by following steps: - step0: Evaluate: \(\sqrt{r+4}+3\) - step1: Substitute: \(\sqrt{12+4}+3\) - step2: Add the numbers: \(\sqrt{16}+3\) - step3: Simplify the root: \(4+3\) - step4: Add the numbers: \(7\) Substitute \( r=x-4 \) into the expression \( \sqrt{r+4}+3 \). Evaluate the expression by following steps: - step0: Evaluate: \(\sqrt{r+4}+3\) - step1: Substitute: \(\sqrt{x-4+4}+3\) - step2: Remove the opposites: \(\sqrt{x}+3\) a. \( f(-4) = 3 \) b. \( f(12) = 7 \) c. \( f(x-4) = \sqrt{x} + 3 \)