Respostas

2014-08-23T15:52:55-03:00
E aí Roberto,

vamos identificar os termos desta P.A.:

~25~~~~~~~~~~~?\\(\underbrace{a_4,a_5,a_6,a_7})\\
~~~~4~termos~~,~~sendo~r=-5~~.\\\\
a_n=a_1+(n-1)r\\
a_{7}=25+(4-1)\cdot(-5)\\
a_{7}=25+3\cdot(-5)\\
a_{7}=25-15\\\\
\Large\boxed{\boxed{a_{7}=10}}.\\.

Tenha ótimos estudos ;D
4 4 4
2014-08-23T15:53:37-03:00
A7=a4+3r =25+3·-5=25-15=10

a7=10
1 5 1