设数列{}是等差数列，数列{}的前项和满足,,且。（1）求数列{}和{}的通项公式：（2）设为数列{．}的前项和，求．
直接写出得数： 3﹣1.2=（0.1）3= 3÷1=×0.4=﹣=×7=+1= 5×÷5×=+×= 21÷3=
直接写得数．×4= 6﹣=÷=×=×=÷=÷=÷=
= 2.5== 1== 1×= 3÷1%==．
×0=×=÷=÷=
直接写得数×8=﹣=÷3= 21×= 2÷=÷=×=+=
}是等差数列，数列{
}的前
项和
满足
,
,
。
为数列{
﹣1.2=（0.1）3= 3÷1
=
×0.4=
﹣
=
×7=
+1
= 5×
÷5×
+
×
= 21
÷3=
×4= 6﹣
=
÷
=
×
×
=
÷
=
÷
=
÷
=
= 2.5
=
= 1
=
= 1
×
= 3÷1%=
=．
×0=
=
=
=
×8=
﹣
=
÷3= 21×
=
=
÷
=
×
=
+
=
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