Solve the Absolute Value Equation: Find x in |2x+4|+x-1=10

Nested Absolute Values with Case Analysis

2x+4+x1=10 |\left|2x+4\right|+x-1|=10

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1

Understand the problem

2x+4+x1=10 |\left|2x+4\right|+x-1|=10

2

Step-by-step solution

To solve the equation 2x+4+x1=10 |\left|2x+4\right|+x-1|=10 , we will consider different cases due to the absolute value expressions.

First, let's set 2x+4+x1=10|2x + 4| + x - 1 = 10:

  • Case 1: 2x+402x + 4 \geq 0 (so 2x+4=2x+4|2x + 4| = 2x + 4),
    Equation becomes: 2x+4+x1=102x + 4 + x - 1 = 10,
    Combine and simplify: 3x+3=103x + 3 = 10,
    Solve: 3x=73x = 7 x=73\Rightarrow x = \frac{7}{3}.
  • Case 2: 2x+4<02x + 4 < 0 (so 2x+4=(2x+4)|2x + 4| = -(2x + 4)),
    Equation becomes: 2x4+x1=10-2x - 4 + x - 1 = 10,
    Combine and simplify: x5=10-x - 5 = 10,
    Solve: x=15-x = 15 x=15\Rightarrow x = -15.

Next, consider 2x+4+x1=10|2x + 4| + x - 1 = -10:

  • Case 3: 2x+402x + 4 \geq 0 (so 2x+4=2x+4|2x + 4| = 2x + 4),
    Equation becomes: 2x+4+x1=102x + 4 + x - 1 = -10,
    Combine and simplify: 3x+3=103x + 3 = -10,
    Solve: 3x=133x = -13 x=133\Rightarrow x = -\frac{13}{3}, which is not a solution since it doesn't satisfy the condition.
  • Case 4: 2x+4<02x + 4 < 0 (so 2x+4=(2x+4)|2x + 4| = -(2x + 4)),
    Equation becomes: 2x4+x1=10-2x - 4 + x - 1 = -10,
    Combine and simplify: x5=10-x - 5 = -10,
    Solve: x=5-x = -5 x=5\Rightarrow x = 5, which is not a solution since it doesn't satisfy the condition.

Thus, the possible solutions are x=732.3x = \frac{7}{3} \approx 2.3 and x=15x = -15.

Therefore, the solution to the problem is x=2.3 x = 2.3 and x=15 x = -15 .

3

Final Answer

x=2.3 x=2.3 , x=15 x=-15

Key Points to Remember

Essential concepts to master this topic
  • Structure: Nested absolute values require systematic case-by-case analysis
  • Method: Set inner expression equal to ±10, then solve each case
  • Verification: Check solutions satisfy original conditions: x=2.3 x = 2.3 and x=15 x = -15

Common Mistakes

Avoid these frequent errors
  • Ignoring the conditions for each case
    Don't solve 2x+4=2x+4 |2x + 4| = 2x + 4 without checking if 2x+40 2x + 4 ≥ 0 = invalid solutions! This leads to extraneous answers that don't work. Always verify each solution satisfies the conditions used to derive it.

Practice Quiz

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\( \left|x\right|=3 \)

FAQ

Everything you need to know about this question

Why do I need to consider both positive and negative cases for the outer absolute value?

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Because A=10 |A| = 10 means A = 10 OR A = -10. You must solve both 2x+4+x1=10 |2x+4| + x - 1 = 10 AND 2x+4+x1=10 |2x+4| + x - 1 = -10 to find all solutions.

How do I know when to use 2x+4=2x+4 |2x+4| = 2x+4 versus 2x+4=(2x+4) |2x+4| = -(2x+4) ?

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Check the sign of the expression inside: if 2x+40 2x + 4 ≥ 0 (meaning x2 x ≥ -2 ), then 2x+4=2x+4 |2x+4| = 2x+4 . If 2x+4<0 2x + 4 < 0 (meaning x<2 x < -2 ), then 2x+4=(2x+4) |2x+4| = -(2x+4) .

Why did some of my solutions get rejected?

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Extraneous solutions happen when your answer doesn't satisfy the original conditions. For example, if you found x=133 x = -\frac{13}{3} using the condition 2x+40 2x + 4 ≥ 0 , but 133<2 -\frac{13}{3} < -2 , then this violates the condition!

Is there an easier way to solve nested absolute value equations?

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Unfortunately, systematic case analysis is the most reliable method. While graphing can help visualize solutions, the algebraic approach ensures you find all solutions and check their validity properly.

How can I check if my final answers are correct?

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Substitute each solution back into the original equation: 2x+4+x1=10 ||2x+4|+x-1| = 10 . For x=73 x = \frac{7}{3} and x=15 x = -15 , both should make the left side equal exactly 10.

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