What type of triangle has side lengths of 4, 7, and 9?

The side lengths form a triangle because 4 + 7 = 11, which is greater than 9. To classify it, compare the square of the longest side with the sum of the squares of the other two: 9² = 81, while 4² + 7² = 65. Since 81 is greater than 65, the triangle is obtuse, so the best answer is C.

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