Question

Write an explicit formula for the sequence 4,-1,-6,-11,-16 then find a14

Answer 1

Try this solution:
1. note, that 4-5=-1; -1-5=-6; -6-5=-11; -11-5=-16, etc.
The suggested sequence is arithmetic, where a₁=4; d=-5.
2. using a₁ and d it is possible to calculate a₁₄=a₁+d(n-1)=a₁-5(14-1)=4-5*13=4-65=-61.

Answer: -61