Question

Determine o número de termos da _5,_9,_17,5........_73

Answer 1

Resposta:

razão: 9/10-2/5=9-4/10=5/10

an=a1+(n-1).r

89/10= 2/5+(n-1).5/10

89/10= 2/5+5/10n-5/10

89/10=4/10+5/10n-5/10

89=4-5+5n

89=-1+5n

89+1=5n

90=5n

90/5=n

n=18