What are the solutions to the inequality [tex]$(x-3)(x+5) \leq 0$[/tex]?

A. [tex]\{x \mid 3 \leq x \leq 5\}[/tex]

B. [tex]\{x \mid -5 \leq x \leq -3\}[/tex]

C. [tex]\{x \mid -5 \leq x \leq 3\}[/tex]

D. [tex]\{x \mid -3 \leq x \leq 5\}[/tex]



Answer :

To solve the inequality [tex]\((x - 3)(x + 5) \leq 0\)[/tex], we will carefully go through each step in detail.

1. Find the roots of the equation:
The inequality [tex]\((x - 3)(x + 5) \leq 0\)[/tex] can be split into finding the roots of the equation [tex]\((x - 3)(x + 5) = 0\)[/tex]. Solving this:

[tex]\[ x - 3 = 0 \quad \text{or} \quad x + 5 = 0 \][/tex]

The solutions are:

[tex]\[ x = 3 \quad \text{and} \quad x = -5 \][/tex]

2. Determine the intervals:
These roots split the number line into three intervals. We need to determine the sign of [tex]\((x - 3)(x + 5)\)[/tex] in each interval:

- Interval 1: [tex]\(x < -5\)[/tex]
- Interval 2: [tex]\(-5 \leq x \leq 3\)[/tex]
- Interval 3: [tex]\(x > 3\)[/tex]

3. Sign Analysis in the intervals:

- For [tex]\(x < -5\)[/tex]:
Choose a test point, e.g., [tex]\(x = -6\)[/tex]:
[tex]\((x - 3)(x + 5) = (-6 - 3)(-6 + 5) = (-9)(-1) = 9\)[/tex], which is positive.

- For [tex]\(-5 \leq x \leq 3\)[/tex]:
Choose a test point, e.g., [tex]\(x = 0\)[/tex]:
[tex]\((x - 3)(x + 5) = (0 - 3)(0 + 5) = (-3)(5) = -15\)[/tex], which is negative.

- For [tex]\(x > 3\)[/tex]:
Choose a test point, e.g., [tex]\(x = 4\)[/tex]:
[tex]\((x - 3)(x + 5) = (4 - 3)(4 + 5) = (1)(9) = 9\)[/tex], which is positive.

4. Include the roots:
Since the inequality is [tex]\(\leq 0\)[/tex], and we have [tex]\((x - 3)(x + 5) = 0\)[/tex] at [tex]\(x = 3\)[/tex] and [tex]\(x = -5\)[/tex], we need to include these points since the inequality allows zero.

5. Form the solution:
The values of [tex]\(x\)[/tex] that satisfy [tex]\((x - 3)(x + 5) \leq 0\)[/tex] are within the interval where the expression is negative, including the points where it equals zero.

Thus, putting this all together, the solution to the inequality [tex]\((x-3)(x+5) \leq 0\)[/tex] is:

[tex]\[ -5 \leq x \leq 3 \][/tex]

Therefore, the correct answer from the given choices is:

[tex]\[ \{x \mid -5 \leq x \leq 3\} \][/tex]

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