Question 20 of 35intermediate🔧 ApplyShort Answer4 marks

Find the domain and range of the following real functions:

(i)

f(x)=−∣x∣f(x) = -|x|

Answer

Domain: R\mathbb{R} (all real numbers)

Range: (−∞,0](-\infty, 0] (all non-positive real numbers)

(ii)

f(x)=9−x2f(x) = \sqrt{9-x^2}.

Answer

Domain: [−3,3][-3, 3]

Range: [0,3][0, 3]

Explanation

For part (i), the modulus function ∣x∣|x| is defined for all real numbers, so its domain is R\mathbb{R}. Since ∣x∣≥0|x| \geq 0 for all xx, multiplying by -1 gives −∣x∣≤0-|x| \leq 0, making the range all non-positive real numbers.

For part (ii), the square root function requires 9−x2≥09-x^2 \geq 0, which gives x2≤9x^2 \leq 9 or −3≤x≤3-3 \leq x \leq 3. The maximum value occurs at x=0x=0 giving 9=3\sqrt{9}=3, and minimum at x=±3x=\pm 3 giving 0=0\sqrt{0}=0.