Question

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Answer 1

Respuesta:

a)

$a_{n} = a_{1} + (n - 1)r$

$r = \frac{a_{8} -a_{5} }{8 - 5} = \frac{25 - 16}{3} = \frac{9}{3} = 3$

$a_{5} = a_{1} + (5- 1)3 \\ 16 = a_{1} + 12 \\ a_{1} = 4$

Término general:

$a_{n} = 4 + (n - 1)3 \\ a_{n} = 3n + 1$

b)

$suma =12( \frac{a_{12} + a_{1} }{2} ) \\ = 6( 37 + 4 ) = 246$