Question

Find the first, fourth, and eighth terms of the sequence.

A(n) = −5 ∙ 2x − 1



–20; –160; –2,560



1; –1,000; –10,000,000



–5; –40; –640



–10; –80; –1,280

Answer 1

-5, -40, -640

Explanation:

`a(n)=-5\cdot2^(n-1)\\\\\text{put n = 1, n = 4 and n = 8 to the expression:}\\\\a(1)=-5\cdot2^(1-1)=-5\cdot2^0=-5\cdot1=-5\\\\a(4)=-5\cdot2^(4-1)=-5\cdot2^3=-5\cdot8=-40\\\\a(8)=-5\cdot2^(8-1)=-5\cdot2^7=-5\cdot128=-640`