The tenth term in the sequence 7, 12, 19, 28. . . . is?

Question

1.) 124

2.) 103

3.) 57

4.) 147

Answer 1

7, 12, 19, 28. . . .

This is neither an Arithmetic Sequence (with a common difference) nor a Geometric Sequence (with a common ratio).

The explicit formula is:

a_n = (n+1)² + 3 [for n≥1]

So, a₁₀ = (10+1)² + 3 = 121 + 3 = 124

You may also calculate the first 10 terms:

How would you find the 100^th term ?

Answer 2

7 + 5 = 12

12 + 7 = 19

19 + 9 = 28

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