函数f（x）=
|
∵函数f（x）=
的定义域为[-1，2]，ax2+bx+2
故ax2+bx+2≥0的解集为[-1，2]，
即-1，2为方程ax2+bx+2=0的两根
由韦达定理可得-1+2=1=-b a
-1×2=-2=2 a
解得a=-1，b=1
故f（x）=
=-x2+x+2
∈[0，-(x+
)2+1 2 9 4
]3 2
故该函数的值域为[0，
]3 2
故答案为：[0，
]3 2
| 选用方框中单词的适当形式完成短文。 | |
has a 3._____ and eats his breakfast. After breakfast he 4._____ his homework. At nine-thirty he 5._____ the number 6 bus to the 6._____ club. He plays basketball 7._____, two hours there. He is usually very 8._____ after that. He 9._____ lunch at twelve. After lunch, he has to(必须) go to the swimming club. Because he has to 10._____ kids with swimming there. |