Respostas

2014-08-17T16:34:46-03:00
E aí mano,

sendo:

a_1=33\\
r=a_2-a_1~\to~r=37-33~\to~r=4

Podemos expressar:

a_8=a_1+7r\\
a_8=33+7\cdot4\\
a_8=33+28\\\\
\large\boxed{\boxed{a_8=61}}\\\\\\
a_{20}=a_1+19r\\
a_{20}=33+19\cdot4\\
a_{20}=33+76\\\\
\large\boxed{\boxed{a_{20}=109}}\\.

ótimos estudos mano!
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