Question

1) Determine o 71° termo da PA (5, 8, 11, 14,..)


2) Dada a PA (7, 12, 17,..492), determine o número de termos (n).​

Answer 1

Resposta:

2)

$a_1=7\\\\r=12-7\\\\r=5\\\\a_n=492\\\\a_1+r(n-1)=a_n\\\\7+5(n-1)=492\\\\5(n-1)=492-7\\\\5(n-1)=485\\\\n-5=485:5\\\\n-5=97\\\\n=97+5\\\\n=102$

1)

$a_1=5\\\\r=8-5=3\\\\a_7_1=a_1+69r\\\\a_7_1=5+69.3\\\\a_7_1=5+207\\\\a_7_1=212$