We are given the absolute value equation:
$$
|x + 3| = |x - 11|
$$
Our goal is to
solve for $ x $. Absolute value equations can be tricky because the expression inside the absolute value can be positive or negative, so we need to consider different cases.
---
🔍 Step 1: Understand What This Equation Means
The equation says that the
distance from $ x $ to $ -3 $ is equal to the
distance from $ x $ to $ 11 $ on the number line.
So, geometrically, we're looking for a point $ x $ that is
equidistant from $ -3 $ and $ 11 $.
That point is the
midpoint between $ -3 $ and $ 11 $.
Let’s compute that:
$$
\text{Midpoint} = \frac{-3 + 11}{2} = \frac{8}{2} = 4
$$
So,
$ x = 4 $ is a solution.
But let's solve it algebraically to confirm and make sure we don’t miss anything.
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✔ Algebraic Solution
We solve:
$$
|x + 3| = |x - 11|
$$
To solve this, we use the property:
> If $ |A| = |B| $, then either $ A = B $ or $ A = -B $
So we set up two cases:
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#### 🔹 Case 1: $ x + 3 = x - 11 $
Subtract $ x $ from both sides:
$$
3 = -11
$$
✘ This is
false, so no solution in this case.
---
#### 🔹 Case 2: $ x + 3 = -(x - 11) $
Simplify the right-hand side:
$$
x + 3 = -x + 11
$$
Add $ x $ to both sides:
$$
2x + 3 = 11
$$
Subtract 3:
$$
2x = 8
$$
Divide by 2:
$$
x = 4
$$
✔ This is a valid solution.
---
🧪 Check the Solution
Plug $ x = 4 $ into the original equation:
Left side: $ |4 + 3| = |7| = 7 $
Right side: $ |4 - 11| = |-7| = 7 $
✔ Both sides are equal. So $ x = 4 $ is correct.
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📌 Final Answer:
$$
\boxed{x = 4}
$$
This is the
only solution.
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💡 Bonus Insight: Why Only One Solution?
Because the absolute value function represents distance. The only point equidistant from $-3$ and $11$ is their midpoint — $4$. There are no other points on the number line equally distant from both.
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Let me know if you'd like to see more example problems! 😊
Parent Tip: Review the logic above to help your child master the concept of computations using absolute value worksheet.