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已知fx=ax^2-c,且-4≤f1≤-1,-1≤f2≤5,则f3的取值范围是?
人气:234 ℃ 时间:2020-06-06 20:12:41
解答
首先,F(3)=9a-c,由-4<=f(1)<=-1,我们得,-4<=a-c<=-1;由-1<=f(2)<=5,我们可得:-1<=4a-c<=5;由这两个不等式我们可得(都是相加,不可以相减),我们解得0<=a<=3,1<=c<=7,所以-7<=9a-c<=26,解得-7<=f(3)<=26
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