设等差数列的公差为(),其前项和为.若,,则的值为________ 答案:【答案】【解析】由已知条件结合等差数列的通项公式和求和公式,可得,求解即可得答案.由,得,解得d=﹣10.故答案为:﹣10.
Jessie felt her life so boring one summer day. She was
tired of watching TV, she read all her books, and her friends were on vacation.
She wanted something different to do. Suddenly, she saw the lawn mower(割草机) sitting in the yard.
“Mom,” she shouted, “I think I will mow the lawn.” Her
mom ran into the yard and said, “Oh no, you don’t. You’re too young to mow the
law.”
“I’m fourteen years old and know how to do it,” Jessie
said. “Besides, it would help Dad out, and he won’t have to worry about it over
the weekend.”
Mom thought for a while and then decided to let Jessie
give it a try. After all, she was home and would keep an eye on her.
Jessie already knew how to start the lawn mower from watching her dad. Jessie
checked the gas(汽油) to make sure it was full, and put on her
gardening gloves to protect her hands. Mom watched from the kitchen window.
Jessie really does know how to mow the lawn. She was very careful around the
flowers and trees. When she finished, she felt so good, but she was so hot. Mom
brought her some ice tea and said, “You sure did a great job. Dad will be very
surprised.”
Later that day, Dad came home and said to Jessie’s
mom, “You didn’t have to mow the lawn. I was going to do it on Saturday. It
looks great. Thanks.”
“I didn’t mow it. Jessie did.”
“Wow, our little girl is growing up!” Dad told Jessie
what a great job she had done.
“It was fun, and I will do it again next week,” said
Jessie.
The neighbor next door came by and asked Jessie if she
wanted to mow his lawn and make some money. “Sure!” said Jessie. Jessie began
mowing his lawn. Two other neighbors asked so, then another three. Jessie was
now mowing lawns for them all and making some money. She was no longer bored!
“I won’t have time to spend my money,” she laughed to herself.
根据材料内容选择最佳答案,并将其标号填入题前括号内。
1.In order to do something different, Jessie decide to
_______.
A.read books B.travel C.mow the lawn D.watch TV
2.What does “keep an eye on” mean?
A.保护 B.注视 C.培养 D.瞄准
3.Before Jessie mowed the lawn, she ______.
A.washed her
hands B.bought some
gas
C.read some
instructions D.put on her
gloves
4.How did Jessie’s father feel when he knew Jessie had
mowed the lawn?
A.Proud. B.Angry. C.Relaxed. D.Worried.
5.What does the text mainly tell us?
A.Neighbors
should learn to help each other.
B.Mowing the
lawn is a good way to make money.
C.Doing
something helpful can make people happy.
D.Children
should help their parents at an early age.