y=-—4^x+(1/2)^1—x+1=-4^x+1/2*(1/2)^(-x)+1=-(2^x)^2+1/2(2^x)+1=-(2^x-1/4)^2+9/8定义域是R由于2^X>0,故当2^X=1/4时,Y有最大值是:9/8故值域(-无穷,9/8]
