A. 42
B. 72
C. 20
D. 58
Explanation:
20 = 42 + 4, 42 = 62 + 6, 58 = 72 + 9, 72 = 82 + 8 and 90 = 92 + 9.
20, 42, 72 and 90 can be expressed in n2 + n form but not 58.
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A. 42
B. 72
C. 20
D. 58
Explanation:
20 = 42 + 4, 42 = 62 + 6, 58 = 72 + 9, 72 = 82 + 8 and 90 = 92 + 9.
20, 42, 72 and 90 can be expressed in n2 + n form but not 58.