已知等差数列{an}的前n项和为Sn.若a3=20-a6,则S8等于 .
80
因为a3=20-a6,
所以S8=4(a3+a6)=4×20=80.
A father was very angry. He said to his son, “How many letters are there in the Alphabet (字母表)?” “I’m sorry, I don’t know.” Answered his son. The father was very angry. He said to his son, You don’t know? You are in school for many years and you don’t know how many letters there are in the Alphabet?” “ No.” answered his son, “But let me ask you a question, Dad. You often go to the post office. Now please tell me how many letters there are in the post office.”
判断正误,写下T或F
小题1:The son didn’t know the meaning of the word “Alphabet”.
小题2:The father was angry because his son was not polite to him.
小题3:The son was too young to go to school, so he couldn’t answer his father’s question.
小题4:The father couldn’t give the right answer to his son’s question.
小题5:The word “letter” has two meanings in English.
小红悄悄地喜欢上了邻居家的一个男孩,一想起他,既甜蜜又自责。你认为下列说法正确的是[ ]
A.这是正常、自然而又美丽的事
B.男女同学间的情感,需要慎重对待、理智处理
C.这种行为是一种极端错误的行为,应予以严厉批评
D.可以尝试进一步发展二人的情感