15,21,39,143,? What is the next term?
Answers
Answer:
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⭐These type of series will be easy to solve, if you're comfortable with perfect squares. Add 1 to each term of the series, then the series changes to:
⭐4(2^2), 16(4^2), 36, 64, the next number in this series should be 10^2
⭐So, the term in our series must be 10^2 - 1 =99
⭐There is also another way to solve this series take the differences
⭐3, 15, 35, 63
⭐First level difference: 12, 20, 28
⭐Second level difference: 8,8
⭐So, the next 2nd level difference must also be 8
⭐Hence, the next 1st level difference must be 28 + 8 = 36
⭐Giving us the next term as 63+36=99
⭐Point to note⚡:
⭐We find that in our series (which is quadratic in nature), the 2nd level difference is constant. This is true for any polynomial series. If, it's a linear series (AP), the first level difference would be constant. If it's a quadratic series, the 2nd level difference would be constant. For a cubic series, the 3rd level difference would be constant, and so on...
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☺️hope it helps you⚡