令a=x^2y^2=4x^2(1-x^2)=4a(1-a)=-4a^2+4a=-4(a-1/升或2)^2+1根号下大于等于02-a>=0,a=x^2>=0则吵猜伍0<=a<=2所以a=1/兆漏2,y^2最大=1a=2,y^2最小=-8则0<=y^2<=1-1<=y<=1值域[-1,1]