Question

quantos termos tem a P.A (17;26;...;197)

Answer 1

a n = a 1 + ( n-1) . r 
197 = 17 + (n-1) . 9 
197 - 17 = ( n-1) . 9 
180 = (n-1) .9 
n -1 = 180 / 9 
n-1 = 20 
n = 20 + 1 
n = 21