Question

Quantos termos tenha PA (15,20,25...160)

Answer 1

r = a2 - a1 = 20-15 = 5

an = a1 + ( n - 1 ) . r

160 = 15 + ( n - 1 ) . 5

160 = 15 + 5n - 5

160 - 10 = 5n

150 = 5n

n = 150/5

n = 30 termos

Answer 2

Quantos termos tenha PA (15,20,25...160)

Fórmula p/ razão :
r=?
r=a2 - a1 = 20 - 15=5



n=> ?
an=>160
r =>5
a1=>15

termo geral :

an=a1+(n-1).r

160=15+(n-1)*5
160=15+5n-5
160-10=5n
150=5n
n=150/5
n=30


R:Quantos termos tenha PA : 30 Termos.