Question

Match the sequence with the correct indicated term.



1)a1 = -4, d= -9, n=20


2)a1 =20, d=4, n=81
3)a12 for 8,3,-2,...

Answers
A)340
B)-47
C)-175
D)94

*PLEASE EXPLAIN*

Answer 1

1) an = a1 + d*(n-1) => a20 = -4 + (-9)*19 = -4 - 171 = - 175
1) ---> C)

2) a81 = 20 + 4*80 = 340;
2) ---> A)

3) a12 = ?
3) ---> B) or D).