y=(1/4)^x-(1/2)^x+1
=(1/2)^(2x)-(1/2)^x+1
设t=(1/2)^x,
y=t²-t+1=(t-1/2)²+3/4
∵x∈[-3,2]∴t∈[1/4,8]
∴当t=1/2时,ymin=3/4
当t=8时,ymax=57
∴函数的值域为[3/4,57]