Respuesta :

ghanami

Answer:

Step-by-step explanation:

hello :

the nth term of an arithmetic sequence is :

An =An+(n-p)d   ....a common difference is : d  

let : n=15    and   p=1    d= 4     A15 =43

A15 = A1 + (15-1)(4)

43= A1 +56

A1= 43-56 = - 13