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1. Find the number of solutions for [tex]$x$[/tex] in the equation [tex]$||x|-1|-2|=3$[/tex].

Sagot :

To solve the equation [tex]\(\left|\left| |x|-1 \right|-2\right| = 3\)[/tex], we need to carefully handle the absolute value functions step-by-step.

### Step-by-Step Solution:

1. Innermost Absolute Value:
[tex]\[ y = |x| - 1 \][/tex]

2. Next Absolute Value:
[tex]\[ z = |y| - 2 = ||x|-1| - 2 \][/tex]

3. Setting up the full equation using the outer absolute value:
[tex]\[ \left|\left| |x|-1 \right|-2\right| = 3 \][/tex]

Breaking it down, we have:
[tex]\[ |z|=3 \implies z = 3 \text{ or } z = -3 \][/tex]

4. Solution for [tex]\(z = 3\)[/tex]:
[tex]\[ ||x|-1|-2 = 3 \][/tex]

This can be further broken down into two cases:
[tex]\[ ||x|-1| - 2 = 3 \text{ or } ||x|-1| - 2 = -3 \][/tex]

Case 1:
[tex]\[ ||x|-1| - 2 = 3 \implies ||x|-1| = 5 \][/tex]
This further splits into two sub-cases:
[tex]\[ |x| - 1 = 5 \implies |x| = 6 \implies x = 6 \text{ or } x = -6 \][/tex]
and
[tex]\[ |x| - 1 = -5 \text{ which has no solution since } |x|-1 \geq 0. \][/tex]

Case 2:
[tex]\[ ||x|-1| - 2 = -3 \implies ||x|-1| = -1 \][/tex]
This also has no solution since [tex]\(||x|-1 \geq 0\)[/tex].

Therefore, from solving [tex]\(||x|-1|-2 = 3\)[/tex], we have:
[tex]\[ x = 6 \text{ or } x = -6 \][/tex]

5. Solution for [tex]\(z = -3\)[/tex]:
[tex]\[ ||x|-1|-2 = -3 \][/tex]

This case also has no solution since [tex]\(|\cdot| - 2 \geq -2\)[/tex].

### Conclusions

By examining the cases, we find that the only valid solutions are:
- [tex]\( x = 6 \)[/tex]
- [tex]\( x = -6 \)[/tex]

Hence, the number of solutions for the equation [tex]\(\left|\left| |x|-1 \right|-2\right| = 3\)[/tex] is [tex]\(2\)[/tex].

### Answer:
[tex]\[ \boxed{2} \][/tex]