二次函数f(x)的二次项系数为负,f(x+2)=f(2-x)
答案:2 悬赏:60
解决时间 2021-02-11 17:25
- 提问者网友:爱你等于作孽
- 2021-02-10 17:07
二次函数f(x)的二次项系数为负,f(x+2)=f(2-x)
最佳答案
- 二级知识专家网友:蜜罐小熊
- 2021-02-10 18:42
由题意可知,对称轴是2,开口向上。
2-(1/2)x^2<=2
2-(1/2)x^2在对称轴左侧或者对称轴上
分三种情况
1:都在对称轴左侧
2-(1/2)x^2>-x^2+6x-7
2:-x^2+6x-7在对称轴右侧
2-[2-(1/2)x^2]<[-x^2+6x-7]-2且-x^2+6x-7>2
3:最低点
2-(1/2)x^2=2
此时-x^2+6x-7=-7
不等式仍然成立
Know from that intended, is the axial symmetry 2, opening up.
2 - (1 / 2) x ^ 2 <= 2
2 - (1 / 2) x ^ 2 symmetry axis in the left or symmetry axis
The three conditions
1: axial symmetry in the left
2 - (1 / 2) x ^ 2>-x ^ 2 +6 x-7
2:-x ^ 2 +6 x-7 in the right symmetry axis
2 - [2 - (1 / 2) x ^ 2] <[-x ^ 2 +6 x-7] -2 and - x ^ 2 +6 x-7> 2
3: the lowest point
2 - (1 / 2) x ^ 2 = 2
At this point - x ^ 2 +6 x-7 =- 7
Inequalities still set up
2-(1/2)x^2<=2
2-(1/2)x^2在对称轴左侧或者对称轴上
分三种情况
1:都在对称轴左侧
2-(1/2)x^2>-x^2+6x-7
2:-x^2+6x-7在对称轴右侧
2-[2-(1/2)x^2]<[-x^2+6x-7]-2且-x^2+6x-7>2
3:最低点
2-(1/2)x^2=2
此时-x^2+6x-7=-7
不等式仍然成立
Know from that intended, is the axial symmetry 2, opening up.
2 - (1 / 2) x ^ 2 <= 2
2 - (1 / 2) x ^ 2 symmetry axis in the left or symmetry axis
The three conditions
1: axial symmetry in the left
2 - (1 / 2) x ^ 2>-x ^ 2 +6 x-7
2:-x ^ 2 +6 x-7 in the right symmetry axis
2 - [2 - (1 / 2) x ^ 2] <[-x ^ 2 +6 x-7] -2 and - x ^ 2 +6 x-7> 2
3: the lowest point
2 - (1 / 2) x ^ 2 = 2
At this point - x ^ 2 +6 x-7 =- 7
Inequalities still set up
全部回答
- 1楼网友:狠傷凤凰
- 2021-02-10 19:43
∵二次函数f(x)的二次项系数,则二次函数图像开口向上
又f(2-x)=f(2+x)
∴x=2是f(x)的对称轴
故对称轴x=2左侧单调递减,右侧单调递增
∵1-2x²<2
1+2x-x²=2-(x-1)²≤2
即1-2x²和1+2x-x²都在对称轴左侧
∴f(1-2x^2)<f(1+2x-x^2),
即1-2x²>1+2x-x²
即x²+2x<0
∴x(x+2)<0
∴-2<x<0
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