Respostas

2013-11-09T19:34:47-02:00
An=a1+(n-1)r
30=a1+(13)r
27=a1+15r

30-13r=A1
27-15r=A1
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30-13r=27-15r
3=-2r
r=-2/3
30-13(-2/3)=A1
30+26/3=a1
116/3=a1

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