A.\(\dfrac{{2x + 6}}{{{x^2} + 1}}\)
B.\(\dfrac{{4x + 2}}{2}\)
C.\(\dfrac{{2x - 4}}{2}\)
D.\(\dfrac{{4x - 2}}{{{x^2} + 1}}\)

A.\(4\)
B.\(2\)
C.\(3\)
D.\(1\)

A.\(14\)
B.\(\sqrt {14} \)
C.\(28\)
D.\(2\sqrt {14} \)

A.\(M = 40,\,\,m = 30\)
B.\(M = 20,\,\,m =  - 2\)
C.\(M = 8,\,\,m =  - 73\)
D.\(M = 10,\,\,m =  - 11\)

A.\(\left\{ { \pm 2i;\,\,\dfrac{1}{2} \pm \dfrac{{\sqrt 3 }}{2}i} \right\}\)
B.\(\left\{ {2i} \right\}\)
C.\(\left\{ { - 2i;\,\, - \dfrac{1}{2} - \dfrac{{\sqrt 3 }}{2}i} \right\}\)
D.\(\left\{ { - 2i;\,\,\dfrac{1}{2} - \dfrac{{\sqrt 3 }}{2}i} \right\}\)

A.\(y = f\left( x \right) =  - {x^3} + 3x + 1\)
B.\(y = f\left( x \right) =  - {x^3} + 3x - 1\)
C.\(y = f\left( x \right) = {x^3} - 3x - 1\)
D.\(y = f\left( x \right) = {x^3} - 3x + 1\)

A.\(\dfrac{{a\sqrt 2 }}{2}\)
B.\(2a\)
C.\(\dfrac{{a\sqrt {15} }}{5}\)
D.\(\dfrac{{a\sqrt 7 }}{7}\)

A.Tam giác \(ABD\) là tam giác đều.
B.Bốn điểm \(A,\,\,B,\,\,C,\,\,D\) tạo thành tứ diện.
C.\(AB\) vuông góc với \(CD\).
D.Tam giác \(BCD\) là tam giác vuông.

A.the figurative meanings of the word culture
B.the distinction between culture and civilization
C.the derivatives of the word culture
D.the multiplicity of meanings of the word culture

A.the figurative meanings of the word culture
B.the distinction between culture and civilization
C.the derivatives of the word culture
D.the multiplicity of meanings of the word culture