A.\(\dfrac{{\sqrt {21} a}}{{14}}\).
B.\(\dfrac{{\sqrt 2 a}}{2}\).
C.\(\dfrac{{\sqrt {21} a}}{7}\).
D.\(\dfrac{{\sqrt 2 a}}{4}\).

A.\(11\).
B.\(9\).
C.\(7\).
D.\(5\).

A.\(\dfrac{2}{5}\)
B.\(\dfrac{{11}}{{20}}\)
C.\(\dfrac{1}{2}\)
D.\(\dfrac{9}{{20}}\)

A.\( - 1\)
B.\( - \dfrac{{18}}{{19}}\)
C.\( - \dfrac{{17}}{{19}}\)
D.\( - \dfrac{{20}}{{19}}\)

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

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

A.\(37m\)
B.\(38m\)             
C.\(39m\)                                   
D.\(30m\)

A.\(\dfrac{3}{2}\)
B.\(\dfrac{{ - 3}}{2}\)
C.\(0\)
D.\(\dfrac{5}{2}\)

A.\(x = 7\)
B.\(x = 21\)
C.\(x = 8\)                                  
D.\(x = 24\)

A.\(\dfrac{{15}}{4}\)
B.\( - \dfrac{{23}}{4}\)
C.\( - \dfrac{{19}}{4}\)           
D.\( - \dfrac{{17}}{4}\)