Oliver and Putri were asked to find an explicit formula for the sequence

-51, -34, -17,0, • .., where the first term should be h (1).
Oliver said the formula is h(n) = —51 + 17n.
Putri said the formula is h (n) = —68 + 17n.
Which one of them is right?

1 answer

To find the explicit formula for the sequence \(-51, -34, -17, 0, \ldots\), we need to determine the pattern in the given terms.

First, let's identify the first term and the common difference:

  1. The first term \(h(1) = -51\).
  2. The second term \(h(2) = -34\).
  3. The third term \(h(3) = -17\).
  4. The fourth term \(h(4) = 0\).

To determine the common difference, we subtract the first term from the second term: \[ -34 - (-51) = -34 + 51 = 17 \] So, the common difference \(d\) is \(17\).

Now, we can describe the \(n\)-th term of an arithmetic sequence using the formula: \[ h(n) = h(1) + (n-1) \cdot d \] Substituting the values we have: \[ h(n) = -51 + (n-1) \cdot 17 \] Simplifying the formula: \[ h(n) = -51 + 17n - 17 \] \[ h(n) = 17n - 68 \]

Now, let's compare this with Oliver's and Putri's formulas:

  • Oliver's formula: \(h(n) = -51 + 17n\)
  • Putri's formula: \(h(n) = -68 + 17n\)

We can see that Oliver's formula simplifies to: \[ h(n) = 17n - 51 \]

This is incorrect because it does not match our derived formula.

On the other hand, Putri's formula: \[ h(n) = -68 + 17n \] can be rearranged to \(h(n) = 17n - 68\), which matches our derived formula.

Therefore, Putri is correct. The correct explicit formula for the sequence is: \[ h(n) = -68 + 17n \]