问题
选择题
若方程x2-3x-1=0的两根分别是x1，x2，则x12+x22的值为（ ）
A．3
B．-3
C．11
D．-11
答案
根据题意得x1+x2=3，x1•x2=-1，
x12+x22=（x1+x2）2-2x1•x2=32-2×（-1）=11．
故选C．
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若方程x2-3x-1=0的两根分别是x1，x2，则x12+x22的值为（ ）
A．3
B．-3
C．11
D．-11
根据题意得x1+x2=3，x1•x2=-1，
x12+x22=（x1+x2）2-2x1•x2=32-2×（-1）=11．
故选C．
| 从方框中选择适当的单词或短语补全短文，每个单词或短语只能使用一次. | |
going somewhere 2._____ . We're going to Hainan. My dad says Hainan is 3._____ than Qingdao, and he says the beaches are 4._____ beautiful. My friend Zhao Fei went to Hainan last year and he said it was a great place 5._____ swmming. Zhao Fei is usually 6._____ swimming, but I'm not. What should I do to enjoy myself? I 7._____ sit on the beach and 8._____ a book. |
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