Giải phương trình

(x+1)^(1/3)+(7-x)^(1/3)=2

Mark the letter A, B, C or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions

He was such a wet blanket at the party tonight!

A. He made people at the party wet through.

B. He spoiled other people's pleasure at the party.

C. He bought a wet blanket to the party.

D. He was wet through when going home from the party.

Giải phương trình  cos   x + cos   3 x = sin   x - sin   3 x .

A .   x = - π 4 + k π 2 k ∈ ℤ

B .   x = π 4 + k π 2 k ∈ ℤ

C .   x = π 4 + k π   k ∈ ℤ

D .   x = π 4 + k 2 π   k ∈ ℤ