21.

Find the first, fourth, and tenth terms of the arithmetic sequence described by the given rule.

A(n) = –3 + (n – 1)(–2.2)

1 answer

To find the first, fourth, and tenth terms of the arithmetic sequence defined by the formula \( A(n) = -3 + (n - 1)(-2.2) \), we can substitute the values of \( n \) into the formula.

  1. First term (n = 1): \[ A(1) = -3 + (1 - 1)(-2.2) \] \[ A(1) = -3 + (0)(-2.2) \] \[ A(1) = -3 + 0 \] \[ A(1) = -3 \]

  2. Fourth term (n = 4): \[ A(4) = -3 + (4 - 1)(-2.2) \] \[ A(4) = -3 + (3)(-2.2) \] \[ A(4) = -3 - 6.6 \] \[ A(4) = -9.6 \]

  3. Tenth term (n = 10): \[ A(10) = -3 + (10 - 1)(-2.2) \] \[ A(10) = -3 + (9)(-2.2) \] \[ A(10) = -3 - 19.8 \] \[ A(10) = -22.8 \]

Thus, the first, fourth, and tenth terms of the arithmetic sequence are:

  • First term: \(-3\)
  • Fourth term: \(-9.6\)
  • Tenth term: \(-22.8\)