41. Is his mother a teacher?

42. Are there two bedrooms in your house?

43. Are you doing the housework at the moment?

44. Was it rainy and wet in Nha Trang yesterday?

45. Do your parents get up early because they have many things to do?

Bài 4

\(x-4\sqrt{x}-1\) \(=\left(x-4\sqrt{x}+4\right)-5=\left(\sqrt{x}-2\right)^2-5\)

Biểu thức đặt min khi \(\left(\sqrt{x}-2\right)^2\text{ m}\text{i}\text{n}\) 

\(\Leftrightarrow\left(\sqrt{x}-2\right)^2=0\Leftrightarrow x=0\)

Vậy y đặt giá trị nhỏ nhất là -5 khi x=0