Question

Determine o 1 termo a7= 17 e R= 5

Answer 1

Utilizando a formula da P.A:

$a_n=a_k+\left(n-k\right)r\\a_7=a_1+\left(7-1\right)5\\17=a_1+\left(6\cdot 5\right)\\17=a_1+30\\a_1=17-30\\\boxed{\bold{a_1=-13}}$