Question

Find the 15th,18th,and,31st terms in the sequence A(n)=2+(n-1)(-2)

Answer 1

Given the sequence

$a_n = 2+(n-1)(-2)=2-2(n-1)=2-2n+2= -2n+4$

You can compute the k-th term by evaluating the generic term at n=k. So, the 15th, 18th and 31st terms are

$a_{15}=-2(15)+4=-30+4=-26$

$a_{18}=-2(18)+4=-36+4=-32$

$a_{31}=-2(31)+4=-62+4=-58$

Answer 2

Substitute the values 15, 18, and 31 into the equation.
A(15)= -26
A(18)= -32
A(31)= -58