已知f（x2+1）=x4+x2-6，则f（x）在定义域内的最小值为（） A．-4_爱下问搜题

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问题选择题

已知f（x²+1）=x⁴+x²-6，则f（x）在定义域内的最小值为（　　）

A．-4

1

4

B．-5

3

4

C．-6

D．-6

1

4

答案

令t=x²+1≥1，则x²=t-1，由于f（x²+1）=x⁴+x²-6，故f（t）=t²-t-6，即f（x）=x²-x-6，x≥1，

由二次函数的性质知f（x）=x²-x-6在[1，+∞）上是增函数，

∴f（x）在定义域内的最小值为f（1）=-6，

故选C

完形填空

We convince ourselves that life will be better once we are married, have a baby, then another. Then we get frustrated because our children are not old enough, and that __1__ will be well when they are older. Then we are frustrated __2__ they reach adolescence and we must deal with them. Surely we’ll be __3__ when they grow out of the teen years.
We tell ourselves our __4__ will be better when our spouse(配偶)gets his/her act together, when we have a nicer car, when we can take a __5__， when we finally retire. The truth is that there is no better time to be happy than __6__.If not, then when? Your life will always be full of challenges. It is better to admit as much and to decide to be happy __7__it all. For the longest time, it seemed that life was about to start—real life.
But there were always some obstacles along the way, an ordeal(苦难) to __8__， some work to be finished, some time to be given, a bill to be __9__.Then life would start. It finally dawned on me that those __10__ were part of life. Little by little, that point of __11__ also helped me see that there isn’t any road to happiness.
Happiness is the road. So, enjoy every moment. And bear in mind that __12__ waits for no one. So stop __13__ school to end, for a return to school, to lose ten pounds, to __14__ ten pounds, for work to begin, to get married，...before deciding to be happy.
Happiness is a voyage, not a destination. There is no __15__ time to be happy than...NOW! Live and enjoy the moment.

B．in addition to

C．in spite of

D．get through

A．achievements

C．waiting for

单项选择题

医学数字图像的实质是（）

A、二维矩阵

B、三维数组

C、灰度图像

D、RGB图像

E、二值图像