If the second term of a geometric sequence is 4 and the third term is −12, find the explicit formula.(1 point)
Responses
an=3⋅(43)n−1
a subscript n baseline equals 3 times left parenthesis Start Fraction 4 over 3 End Fraction right parenthesis superscript n minus 1 baseline
an=43⋅(3)n−1
a subscript n baseline equals Start Fraction 4 over 3 End Fraction times left parenthesis 3 right parenthesis superscript n minus 1 baseline
an=−43⋅(−3)n−1
a subscript n baseline equals negative Start Fraction 4 over 3 End Fraction times left parenthesis negative 3 right parenthesis superscript n minus 1 baseline
an=−3⋅(−43)n−1
aₙ = 4 ⋅(-3)^(n-1)
a r^(n-1)
a r^1 = 4
a r^2 = -12
so
r = -12/4 = -3
a *(-3) = 4
a = -4/3
so Tn = -4/3 * (-3)^(n-1)