Solve |4x - 5| ≤ 2x + 9: Absolute Value Inequality Challenge

Question

Given:

4x52x+9 \left|4x - 5\right| \leq 2x + 9

Which of the following statements is necessarily true?

Step-by-Step Solution

Let's solve the inequality: 4x52x+9 \left|4x - 5\right| \leq 2x + 9 .

This splits into two cases:

(1) 4x52x+9 4x - 5 \leq 2x + 9 and (2) 4x5(2x+9) 4x - 5 \geq -(2x + 9) .

For inequality (1):

4x52x+9 4x - 5 \leq 2x + 9

Subtract 2x 2x from both sides:

2x59 2x - 5 \leq 9

Add 5 to both sides:

2x14 2x \leq 14

Divide both sides by 2:

x7 x \leq 7

For inequality (2):

4x52x9 4x - 5 \geq -2x - 9

Add 2x 2x to both sides:

6x59 6x - 5 \geq -9

Add 5 to both sides:

6x4 6x \geq -4

Divide both sides by 6:

x23 x \geq -\frac{2}{3}

Combining both solutions gives us 23x7 -\frac{2}{3} \leq x \leq 7 .

Answer

23x7 -\frac{2}{3} \leq x \leq 7