A.\(2y' + xy'' =  - \dfrac{1}{{{x^2}}}\)
B.\(y' + xy'' = \dfrac{1}{{{x^2}}}\)
C.\(y' + xy'' =  - \dfrac{1}{{{x^2}}}\)
D.\(2y' + xy'' = \dfrac{1}{{{x^2}}}\)

A.\(V = \dfrac{{\pi {a^3}}}{4}\)
B.\(V = \pi {a^3}\)
C.\(V = \dfrac{{\pi {a^3}}}{6}\)
D.\(V = \dfrac{{\pi {a^3}}}{2}\)

A.\(S = 2\)
B.\(S =  - 2\)
C.\(S = 0\)
D.\(S = 1\)

A.\(l = \dfrac{{\sqrt 5 a}}{2}\)
B.\(l = 2\sqrt 2 a\)
C.\(l = \dfrac{{3a}}{2}\)
D.\(l = 3a\)

A.Điểm N
B.Điểm Q
C.Điểm E
D.Điểm P

A.\(I = 2\int\limits_0^3 {\sqrt u du} \)
B.\(I = \int\limits_1^2 {\sqrt u du} \)
C.\(I = \int\limits_0^3 {\sqrt u du} \)
D.\(I = \dfrac{1}{2}\int\limits_1^2 {\sqrt u du} \)

A.\(y = \dfrac{{2x + 3}}{{x + 1}}\)
B.\(y = \dfrac{{2x - 1}}{{x + 1}}\)
C.\(y = \dfrac{{2x - 2}}{{x - 1}}\)
D.

A.\(S = \left\{ { - 3;3} \right\}\)
B.\(S = \left\{ 4 \right\}\)
C.\(S = \left\{ 3 \right\}\)
D.\(S = \left\{ { - \sqrt {10} ;\sqrt {10} } \right\}\)

A.\(S = b - a\)
B.\(S = b + a\)
C.\(S =  - b + a\)
D.\(S =  - b - a\)

A.6
B.10
C.12
D.