số quyển sách bạn Lan mua hết số tiền là:

120000.3=360000[đồng]

10% số tiền của hóa đơn là:

350000x10%=35000[đồng]

bạn lan đc trả lại số tiền là:

350000-35000=315000[đồng]

1²+2²+3²+...+10²=385

Tính A=3²+6²+9²+...+30²

           =3²+[2.3]²+[3.3]²+...+[3.10]²

           =3²+2².3²+3².3²+...+3².10²

                 ⁼3².[1²+2²+3²+...+10^2]

                 ⁼3².385[vì 1²+2²+3²+...+10²+385

              =9.385

               =3465

1²+2²+3²+...+10²=385

Tính A=3²+6²+9²+...+30²

           =3²+[2.3]²+[3.3]²+...+[3.10]²

           =3²+2².3²+3².3²+...+3².10²

                 ⁼3².[1²+2²+3²+...+10^2]

                 ⁼3².385[vì 1²+2²+3²+...+10²+385

              =9.385

               =3465

Hello,
 I live in Uong Bi city at Quang Ninh province.My house have a big yard.There is also a glass roof.My best friend has long black hair and black eyes.My best friend very like to read a book and listen her favorite music.She is very kind and funny.I really like to talking with her.Because her story is very interesting.I sometimes help my classmates with their homework.Before Tet,I go to my grandmother to package Chung cake with my grandmother and my grandfather.I sometimes go home before my mom and my dad.

my neighbourhood is opposite my house.i can see many things in my neighbourhood.There are some peachs in her fridge.She always have many candy and cookies.My neighbourhood are very like to go shopping and eat out.She go shopping five times a week.I very like to living in my neighbourhood.Because she have many foods and soda.And she is very kind and gentle.I can look at Chung cake with her when Tet.

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