-3<=log[0.5]x<=-0.5√2≤x≤8y=(log[2]x/2)(log[2]x/4)={log[2]x}^2-3log[2]x+2={log[2]x-3/2}^2-1/4x=2√2,y的最小值-1/4x=√2,y的最大值6