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

A.vô số.
B.1
C.2
D.0

A.\({45^0}\)
B.\({60^0}\)
C.\({30^0}\)
D.\({90^0}\)

A.\( - \dfrac{5}{3}\)
B.1
C.\( - \dfrac{1}{3}\)
D.\( - 1\)

A.\({S_{xq}} = 2\pi {R^2}\)
B.\({S_{xq}} = 2\pi Rl\)
C.\({S_{xq}} = \pi Rl\)
D.\({S_{xq}} = \dfrac{4}{3}\pi {R^3}\)

A.\(\dfrac{{7!}}{{3!}}\)
B.\(A_7^3\)
C.21
D.\(C_7^3\)

A.9
B.4
C.36
D.\(\dfrac{1}{4}\)

A.\(\int\limits_2^9 {f\left( x \right)dx =  - 1} \)
B.\(\int\limits_2^9 {f\left( x \right)dx = 20} \)
C.\(\int\limits_2^9 {f\left( x \right)dx =9 } \)
D.\(\int\limits_2^9 {f\left( x \right)dx = 1} \)

A.\(z = 1 + 2i\)
B.\(z = 2 + i\)
C.\(z = 1 - 2i\)
D.\(z =  - 2 + i\)

A.\(y =  - \dfrac{1}{4}\)
B.\(x =  - 1\)
C.\(y = \dfrac{1}{2}\)
D.\(x = 2\)