Question

Determine o numero de termos da P.A (2,7/3,8/3,...,18) a)49 termos ? b)46 termos ? c)47 termos ? d)44 termos ? e)43 termos ?

Answer 1

a1 = 2/1

a2 = 7/3

a3 = 8/3

an = 18

r = 8/3 - 7/3 = 1/3 ****

an = a1 + ( n - 1)r

18 = 2 + ( n - 1) * 1/3

18 -2 = ( n/3 - 1/3 )

n/3 - 1/3 = 16/1

n/3 = 16/1 + 1/3

n/3 = ( 48 + 1)/3 ou 49/3

n/3 = 49/3

multiplica cruzado

3 * n = 49 * 3

3n = 147

n = 147/3 = 49 termos *** ( a )