JAMB 2013 Mathematics · Question 17

Evaluate 3(x + 2) > 6(x + 3)

Options

  1. A.x < 4
  2. B.x > -4
  3. C.x < -4
  4. D.x > 4

Answer: C. x < -4

Explanation written with AI and checked against the answer key

Analysis

We are asked to solve a linear inequality. The goal is to isolate the variable xx on one side of the inequality sign to determine its range of values.

Concept

When solving inequalities, the rules are very similar to solving equations, with one critical exception: if you multiply or divide both sides by a negative number, you must reverse the inequality sign.

Step-by-Step Solution

Step 1: Expand the brackets Distribute the numbers outside the parentheses: 3(x)+3(2)>6(x)+6(3)3(x) + 3(2) > 6(x) + 6(3) 3x+6>6x+183x + 6 > 6x + 18

Step 2: Group the like terms Move the xx terms to one side and the constant numbers to the other. Let's move 3x3x to the right and 1818 to the left: 6−18>6x−3x6 - 18 > 6x - 3x

Step 3: Simplify both sides −12>3x-12 > 3x

Step 4: Solve for xx Divide both sides by 33: −123>3x3\frac{-12}{3} > \frac{3x}{3} −4>x-4 > x

This can also be written as: x<−4x < -4

Conclusion

By simplifying the inequality, we found that xx must be less than −4-4. This matches option C.

Exam Tip

When you have an inequality like a>ba > b, it is exactly the same as b<ab < a. If you ever feel confused about which way the sign should face, read it out loud: "−4-4 is greater than xx" is the same as saying "xx is less than −4-4." Always double-check your sign direction after dividing by a negative number!

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