CR Algebra 2 A (GP) 23-24 / 1: Tools of Algebra

What is the solution of [tex]\frac{1}{3}|3x + 9| - 5 = 4[/tex]?

A. [tex]x = 6[/tex] or [tex]x = -12[/tex]

B. [tex]x = -6[/tex] or [tex]x = 0[/tex]

C. [tex]x = 0[/tex] or [tex]x = 6[/tex]

D. [tex]x = -\frac{4}{3}[/tex] or [tex]x = 0[/tex]



Answer :

To solve the equation [tex]\(\frac{1}{3}|3x + 9| - 5 = 4\)[/tex], we need to isolate [tex]\(x\)[/tex]. Here is the step-by-step approach:

1. Start with the given equation:
[tex]\[ \frac{1}{3}|3x + 9| - 5 = 4 \][/tex]

2. Isolate the absolute value term:
To do that, first add 5 to both sides:
[tex]\[ \frac{1}{3}|3x + 9| = 9 \][/tex]

3. Eliminate the fraction:
Multiply both sides by 3 to get rid of the fraction:
[tex]\[ |3x + 9| = 27 \][/tex]

4. Solve the absolute value equation:
The equation [tex]\(|3x + 9| = 27\)[/tex] can be split into two separate equations:
[tex]\[ 3x + 9 = 27 \quad \text{and} \quad 3x + 9 = -27 \][/tex]

5. Solve each equation separately:

For [tex]\(3x + 9 = 27\)[/tex]:
[tex]\[ 3x + 9 = 27 \][/tex]
Subtract 9 from both sides:
[tex]\[ 3x = 18 \][/tex]
Divide both sides by 3:
[tex]\[ x = 6 \][/tex]

For [tex]\(3x + 9 = -27\)[/tex]:
[tex]\[ 3x + 9 = -27 \][/tex]
Subtract 9 from both sides:
[tex]\[ 3x = -36 \][/tex]
Divide both sides by 3:
[tex]\[ x = -12 \][/tex]

6. Verify the solutions:
We have found [tex]\(x = 6\)[/tex] and [tex]\(x = -12\)[/tex]. To verify, substitute these values back into the original equation:

For [tex]\(x = 6\)[/tex]:
[tex]\[ \frac{1}{3}|3(6) + 9| - 5 = \frac{1}{3}|18 + 9| - 5 = \frac{1}{3}|27| - 5 = 9 - 5 = 4 \][/tex]
This checks out.

For [tex]\(x = -12\)[/tex]:
[tex]\[ \frac{1}{3}|3(-12) + 9| - 5 = \frac{1}{3}|-36 + 9| - 5 = \frac{1}{3}|-27| - 5 = 9 - 5 = 4 \][/tex]
This also checks out.

Therefore, the solution to the equation [tex]\(\frac{1}{3}|3x + 9| - 5 = 4\)[/tex] is:
[tex]\[ x = 6 \quad \text{or} \quad x = -12 \][/tex]

The correct answer is:
[tex]\[ x = 6 \text{ or } x = -12 \][/tex]