Question
15 12 5 ? -21
-40 What should come in place of the question mark (?) in the following number series?Solution
15 + 1² - 2² = 12 12 + 3² - 4² = 5 5 + 5² - 6² = -6 - 6 + 7² - 8² = -21 - 21 + 9² - 10² = -40
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