已知x为实数,则x乘以根号下(4-x平方)的取值范围是?

题目

已知x为实数,则x乘以根号下(4-x平方)的取值范围是?

答案

y=f(x)=x*(4-x^2)^(1/2)
y^2=x^2*(4-x^2)<=[(x^2+4-x^2)/2]^2=4
-2<=y<=2