Question

Write an explicit formula for the sequence 8,3,-2,-7,-12… then find a14

Answer 1

This is an arithmetic progression with common difference, d= -5 and first term, a=8
Tn= a+(n-1)d
Tn= 8+ (n-1) * -5
Tn= 8+-5(n-1)
Tn= 8-5n+5
Explicit Formula: Tn= -5n+13  
a14= -5(14)+13
= -70+13
= -57