The set A = {x : x is a positive integer and x² < 40} in roster form is:

A{0, 1, 2, 3, 4, 5, 6}

B{1, 2, 3, 4, 5, 6, 7}

C{1, 2, 3, 4, 5, 6}

D{1, 2, 3, 4, 5}

Answer & Solution

Correct answer: C. {1, 2, 3, 4, 5, 6}

Positive integers x with x² < 40: 1, 4, 9, 16, 25, 36 — all < 40 7² = 49 > 40. So x ∈ {1, 2, 3, 4, 5, 6}. Note x is a POSITIVE integer so 0 is excluded.

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