maihuna wrote:||x-9| -3| = 6 has how many solutions:
0
1
2
3
4
I'd also use a 'distance' approach here, but there is one important observation we need to make - |x - 9| can't be negative. If we let y = |x - 9| and look at an equation like the following:
|y - 3| = 6
then the distance between y and 3 is equal to 6, so y can only be -3 or 9. So y = |x - 9| = -3, or |x - 9| = 9. Since it's impossible for |x - 9| to be negative, the only possibility is that |x - 9| = 9, or that "the distance between x and 9 is 9". So x could be 0 or 18, and we have two solutions.
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