Answer:
Step-by-step explanation:
Arithmetic sequaence:
[tex]\sf a_n = -3(4)^n - 1\\\\a_1=-3*4^1 -1\\\\ = -3*4 - 1\\\\ = -12 - 1\\\\a_1=-13[/tex]
[tex]a_2 = -3*4^2-1\\[/tex]
= -3*16 -1
= -48 - 1
= -49
difference = second term - first term
= -49 -(-13)
= -49 + 13
d = -36
[tex]\boxed{S_n=\dfrac{n}{2}[2a + (n-1)d]}[/tex]
[tex]\sf S_5=\dfrac{5}{2}*[2*(-13} + 4*(-36)]\\\\ =\dfrac{5}{2}[-26-144]\\\\=\dfrac{5}{2}*(-270)[/tex]
= 5*(-135)
= -675
