What is the next term in the series? -1,4,21,56,?
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116
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114
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117
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115
Reveal answer
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Correct answer
Explanation
The differences between terms are: 4 - (-1) = 5, 21 - 4 = 17, 56 - 21 = 35. The second differences are: 17 - 5 = 12, 35 - 17 = 18. The third difference is 6. Next second difference is 18 + 6 = 24. Next first difference is 35 + 24 = 59. Next term is 56 + 59 = 115.
AI explanation
The differences between the terms are 5, 17, and 35, whose second differences are 12 and 18. Continuing this pattern of increasing differences, the next second difference is 24, making the next first difference 59; adding this to 56 gives 115.