9^x-10*3^x+9小于等于0,求y=(1/4)^(x-1)-4(1/2)^x=2的最值,并求出相对应的x的值

令a=3^x
a^2-10a+9<=0
(a-1)(a-9)<=0
1<=a<=9
3^0<=3^x<=3^2
0<=x<=2

y=(1/4)^(x-1)-4*(1/2)^x+2
=(1/4)^x/(1/4)-4*(1/2)^x+2
=4*(1/4)^x-4*(1/2)^x+2
令b=(1/2)^x
0<=x<=2
所以(1/2)^2<=(1/2)^x<=(1/2)^0
1/4<=m<=1
y=4m^2-4m+2
=4(m-1/2)^2+1
所以m=1/2,y最小=1，(1/2)^x=1/2，x=1
m=1，y最大=2，(1/2)^x=1，x=0

综上
x=0,y最大=2
x=1,y最小=1