Answer:
0 or 1
Explanation:
The answer to this depends on the version of the triangle inequality your author uses.
If you require ...
4 + 5 > 9 . . . . . false; NO TRIANGLES can be constructed
On the other hand, if you allow ...
4 + 5 ≥ 9 . . . . . true; ONE TRIANGLE can be constructed
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Please consult your lesson materials to see which answer is expected.
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Comment on a 4, 5, 9 triangle
A "triangle" with sides of lengths 4, 5, and 9 will look like a line segment. It will have zero height, hence zero area. Some authors don't consider such a figure to be a triangle.