A.\(a + b.\)
B.\(\frac{{ab}}{{a + b}}.\)
C.\(\frac{{a + b}}{{ab}}.\)
D.\({a^2} + {b^2}.\)

A.\(2\)
B.\(8\)  
C.\(4\)  
D.\(6\)

A.\(\frac{{x - 1}}{{ - 2}} = \frac{{y + 3}}{4} = \frac{{z + 2}}{{ - 1}}.\)
B.\(\frac{{x - 1}}{2} = \frac{{y + 3}}{{ - 4}} = \frac{{z + 2}}{1}.\)
C.\(\frac{{x + 1}}{2} = \frac{{y - 3}}{{ - 4}} = \frac{{z - 2}}{1}.\)
D.\(\frac{{x - 2}}{1} = \frac{{y + 4}}{{ - 1}} = \frac{{z + 1}}{3}.\)

A.\({u_n} = 5\left( {n - 1} \right).\)
B.\({u_n} = {5^{n + 1}}\)
C.\({u_n} = 5\left( {n + 1} \right).\)
D.\({u_n} = 5n + 1.\)

A.\(\frac{{3\pi }}{2}\)
B.\(\frac{\pi }{2}\)
C.\(\pi \)
D.\(\frac{{5\pi }}{2}\)

A.30
B.20
C.10
D.5

A.\(1\) .
B.\(0\).
C.\(3\)  .
D.\(2\).

A.\(A\left( {1;2; - 1} \right)\).
B.\(A\left( {3;2; - 1} \right)\).
C.\(A\left( {3; - 2; - 1} \right)\).
D.\(A\left( { - 3; - 2;1} \right)\).

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

A.\(\left( { - \infty ;6} \right)\).
B.\(\left( { - \infty ;8} \right)\).
C.\(\left( {0;8} \right)\) .
D.\(\left( {8; + \infty } \right)\) .