Chứng minh \(\dfrac{1}{x^2+y+z}+\dfrac{1}{y^2+z+x}+\dfrac{1}{z^2+x+y}\ge\dfrac{3}{x+y+z}\)

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.

He did not remember the meeting. He went out for a coffee with his friends then.

A. Not remember the meeting, he went out for a coffee with his friends.

B. Not to remember the meeting, he went out for a coffee with his friends.

C. Not remembered the meeting, he went out for a coffee with his friends.

D. Not remembering the meeting, he went out for a coffee with his friends.

Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the underlined word(s) in each of the following questions.

I’d rather stay in a hotel with all the amenities than camp in the woods.

A. expenses

B. friends

C. sports

D. conveniences

Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions.

She was unhappy that she lost contact with a lot of her old friends when she went abroad to study.

A. put in charge of 

B. got in touch with

C. lost control of

D. made room for

Hình bên cho biết Ox, Oy là hai tia đối nhau, x O z ^ = 30 ∘ ,   y O t ^ = 60 ∘ ,  tia Ot nằm giữa hai tia Oy và Ox Hãy tính số đo góc  z O t ^ .