a, Cho a,b > 0. Cm: \(\dfrac{1}{ab}\ge\dfrac{4}{\left(a+b\right)^2}\) b, Tìm GTNN của A=\(\dfrac{1}{x^2+y^2}+\dfrac{2}{xy}+4xy\) (với x,y>0 và \(x+y\le1\)

Cho: x,y>0 thoả mãn x+y=1.

Chứng minh: \(\dfrac{1}{x^2}+\dfrac{1}{y}-\dfrac{2}{xy}\ge16\)

Mr. Brown is a good teacher.

A. Mr. Brown teaches very good.

B. Mr. Brown teaches very well.

C. Mr. Brown is very well teacher.

D. Mr. Brown is teaching very well.

Mark the letter A, B, C or D on your answer sheet to show the underlined part that needs correction in each of the following questions.

Many young people lack skills, good education, and financial to settle in the urban areas where many jobs are found.

A. Urban areas

B. financial

C. are found

D. the most