Solve the Absolute Value Equation: Balancing |x-1| and |2x+3|

Absolute Value Equations with Two Cases

x1=2x+3 |x-1|=|2x+3|

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1

Understand the problem

x1=2x+3 |x-1|=|2x+3|

2

Step-by-step solution

To solve the equation x1=2x+3 |x-1| = |2x+3| , follow these steps:

  • First, recall the property: for any real numbers a a and b b , a=b |a| = |b| implies a=b a = b or a=b a = -b .
  • We will consider two cases based on this property:

Case 1: Assume x1=2x+3 x-1 = 2x+3 .
Simplify the equation:
x1=2x+3 x-1 = 2x+3
Subtract x x from both sides:
1=x+3 -1 = x+3
Subtract 3 from both sides:
x=4 x = -4 .

Case 2: Assume x1=(2x+3) x-1 = -(2x+3) .
Simplify the equation:
x1=2x3 x-1 = -2x-3
Add 2x 2x to both sides:
3x1=3 3x-1 = -3
Add 1 to both sides:
3x=2 3x = -2
Divide everything by 3:
x=23 x = -\frac{2}{3} .

Therefore, the solutions to the equation x1=2x+3 |x-1| = |2x+3| are x=4 x = -4 and x=23 x = -\frac{2}{3} .

These solutions correspond to answer choice 4: x=4 x = -4 , x=23 x = -\frac{2}{3} .

Thus, x=4 x = -4 and x=23 x = -\frac{2}{3} .

3

Final Answer

x=4 x=-4 , x=23 x=-\frac{2}{3}

Key Points to Remember

Essential concepts to master this topic
  • Property: |a| = |b| means a = b or a = -b
  • Technique: Solve x-1 = 2x+3 gives x = -4, then x-1 = -(2x+3) gives x = -2/3
  • Check: |-4-1| = |2(-4)+3| becomes 5 = 5 ✓

Common Mistakes

Avoid these frequent errors
  • Solving only one case and missing the second solution
    Don't solve just x-1 = 2x+3 and stop = missing half the solutions! Absolute value equations create two separate cases because |a| = |b| has two possibilities. Always solve both a = b AND a = -b to find all solutions.

Practice Quiz

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\( \left|x\right|=5 \)

FAQ

Everything you need to know about this question

Why do I need to solve two separate equations?

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Because absolute value makes expressions positive! When x1=2x+3 |x-1| = |2x+3| , the expressions inside could be equal OR opposite. That's why we get two cases to solve.

How do I know which case to solve first?

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It doesn't matter! You can solve Case 1: x-1 = 2x+3 or Case 2: x-1 = -(2x+3) in any order. Just make sure you solve both cases.

What if one of my solutions doesn't work when I check it?

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Sometimes absolute value equations produce extraneous solutions. Always substitute each answer back into the original equation. If it doesn't make both sides equal, discard that solution.

Can absolute value equations have no solutions?

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Yes! Sometimes neither case produces a valid solution. That's why checking your work is crucial - it tells you which solutions are real and which are extraneous.

Why is the second case x-1 = -(2x+3) instead of -(x-1) = 2x+3?

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Both work! The property a=b |a| = |b| means a = b OR a = -b. You could write it as x-1 = -(2x+3) or -(x-1) = 2x+3 - they're equivalent and give the same answer.

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