Respuesta :
Short Answer: an = a1 + (n - 1) * d where a1 = - 9 and d = 7
Formula
an = a1 + (n - 1)*7 We have to try it.
Givens
a4 = ??
a1 = - 9
n = 4
d = 7
Sub and solve
a4 = - 9 + (4 - 1)*7
a4 = - 9 + 3*7
a4 = - 9 + 21
a4 = 12 which seems to check.
Answer an = a1 + (n - 1)*d
Formula
an = a1 + (n - 1)*7 We have to try it.
Givens
a4 = ??
a1 = - 9
n = 4
d = 7
Sub and solve
a4 = - 9 + (4 - 1)*7
a4 = - 9 + 3*7
a4 = - 9 + 21
a4 = 12 which seems to check.
Answer an = a1 + (n - 1)*d