数学题|x-(a+1)^2/2|

来源:学生作业帮助网 编辑:作业帮 时间:2024/05/05 22:00:37

数学题|x-(a+1)^2/2|
数学题|x-(a+1)^2/2|

数学题|x-(a+1)^2/2|
x^2-3(a+1)x+2(3a+1)=(x-2)(x-(3a+1))

一式得2a≤x≤a^2+1
二式得(x-2)(x-3a-1)≤0
(1)a<1/3,则解为3a+1≤x≤2
得3a+1≤2a 且a^2+1≤2
得a=-1
(2)a=1/3不成立
(3)a>1/3则解为2≤x≤3a+1
2≤2a且a^2+1≤3a+1
得1≤a≤3
所以a=-1或1≤a≤3

1 -(a-1)^2/2 <= x-(a+1)^2/2 <= (a-1)^2/2
2a = -(a-1)^2/2 +(a+1)^2/2 <= x <= (a-1)^2/2+(a+1)^2/2= a^2 +1
2a <= x <= a^2 +1
2 (x-1.5(a+1) )^2 <= 长度受限,自己解2吧

前面不等式的解集是后面不等式的子集
由于(a-1)^2/2>=0,前面的解集是
-(a-1)^2/2= 2a=后面的
x^2-3(a+1)x+2(3a+1)=[x-(3a+1)](x-2)<=0
然后讨论3a+1与2的关系,求解

由已知得:2a≤x≤a^2+1
又(x-2)[x-(3a+1)]≤0 ⑴
两种情况:2≤2a且3a+1≥a^2+1,2≤3a+1,解得:1≤a≤3
或3a+1≤2a且a^2+1≤2,2≥3a+1,解得:a=-1
故a=-1或1≤a≤3

|x-(a+1)^2/2|<=(a-1)^2/2的解2a <= x <= a^2+1
x1=3a+1, x2=2
(1)a^2+1 <=2 ,-1<=a<=1; 3a+1<=2a , a<=-1; a=-1
(2) a^2+1<=3a+1,0<=a<=3;2a>=2 , a>=1;1<=a<=3
所以: 1<=a<=3且a=-1