JAMB 2023 Mathematics · Question 16

Solve for x: 3(x – 1) ≤ 2 (x – 3)

Options

  1. A.x ≤ -3
  2. B.x ≥ -3
  3. C.x ≤ 3
  4. D.x ≥ 3

Answer: A. x ≤ -3

Explanation written with AI and checked against the answer key

Analysis

This is a linear inequality problem. The goal is to isolate the variable xx on one side of the inequality sign, similar to how you would solve a linear equation, while being mindful of the rules regarding inequality signs.

Concept

To solve linear inequalities:

  1. Expand the brackets: Use the distributive property to multiply the terms inside the parentheses.
  2. Collect like terms: Move all terms containing xx to one side and constant numbers to the other.
  3. Simplify: Combine the terms.
  4. Solve for xx: If you divide or multiply by a negative number, remember to flip the inequality sign. In this case, we will see if that is necessary.
Step-by-Step Solution

Step 1: Expand the brackets Given: 3(x−1)≤2(x−3)3(x - 1) \leq 2(x - 3)

Multiply 33 by (x−1)(x - 1) and 22 by (x−3)(x - 3): 3x−3≤2x−63x - 3 \leq 2x - 6

Step 2: Collect like terms Subtract 2x2x from both sides to bring the xx terms to the left: 3x−2x−3≤−63x - 2x - 3 \leq -6 x−3≤−6x - 3 \leq -6

Step 3: Isolate xx Add 33 to both sides of the inequality: x≤−6+3x \leq -6 + 3 x≤−3x \leq -3

Conclusion

After simplifying the inequality, we arrive at x≤−3x \leq -3. This matches option A.

Exam Tip

When solving inequalities, always double-check your signs. A common mistake students make is forgetting to flip the inequality sign when dividing by a negative number (e.g., if you had −x≤3-x \leq 3, it would become x≥−3x \geq -3). In this specific problem, we did not need to flip the sign because the coefficient of xx remained positive.

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