问题
解答题
已知x=
（1）x2-y2 （2）x2+y2． |
答案
（1）∵x=
+3
，y=2
-3
，2
∴x2-y2=（x+y）（x-y）=2
×23
）=42
；6
（2）∵x=
+3
，y=2
-3
，2
∴x+y=2
，xy=1，3
则x2+y2=（x+y）2-2xy=12-2=10．
搜题请搜索小程序“爱下问搜题”
已知x=
（1）x2-y2 （2）x2+y2． |
（1）∵x=
+3
，y=2
-3
，2
∴x2-y2=（x+y）（x-y）=2
×23
）=42
；6
（2）∵x=
+3
，y=2
-3
，2
∴x+y=2
，xy=1，3
则x2+y2=（x+y）2-2xy=12-2=10．
| 从方框中选择合适的单词，并用其正确形式填空。 | |
term is a chance to take up new hobbies. Most schools offer 3. kinds of hobby classes. Students take them in their free periods or after school. Some classes you have to 4. for and others are free(免费的). For example, I once 5. a free Wednesday evening gymnastics class my school offered. But when I learnt how 6. the drum(鼓) my parents had to pay for the lessons. The most popular extra classes at my school were piano lessons and drama club. Both classes offered 7. that students could take. Students with many hobbies sometimes felt more stressed than those 8. any one. But the students with 9. left school with many extra skills. I haven't cont inued any of the hobbies I 10. at school. But I have never regretted taking them, because hobbies are also a way of making friends. My best friend today is someone I met in my gymnastics class. |