Giải phương trình \({x^2} + \frac{{{x^2}}}{{{{\left( {x + 1} \right)}^2}}} = 1\).
A.\(\left[ \begin{array}{l}{x_1} = \frac{{\sqrt 2 + 1 + \sqrt {2\sqrt 2 - 1} }}{2}\\{x_2} = \frac{{\sqrt 2 + 1 - \sqrt {2\sqrt 2 - 1} }}{2}\end{array} \right.\)
B.\(\left[ \begin{array}{l}{x_1} = \frac{{\sqrt 2 - 1 + \sqrt {2\sqrt 2 - 1} }}{2}\\{x_2} = \frac{{\sqrt 2 - 1 - \sqrt {2\sqrt 2 - 1} }}{2}\end{array} \right.\)
C.\(\left[ \begin{array}{l}{x_1} = \frac{{\sqrt 2 - 1 + \sqrt {2\sqrt 2 + 1} }}{2}\\{x_2} = \frac{{\sqrt 2 - 1 - \sqrt {2\sqrt 2 + 1} }}{2}\end{array} \right.\)
D.\(\left[ \begin{array}{l}{x_1} = \frac{{\sqrt 2 + 1 + \sqrt {2\sqrt 2 + 1} }}{2}\\{x_2} = \frac{{\sqrt 2 + 1 - \sqrt {2\sqrt 2 + 1} }}{2}\end{array} \right.\)

Tính giá trị của biểu thức \(A\) khi \(x = 25.\)
A.\(A=15\)
B.\(A=5\)
C.\(A=10\)
D.\(A=12\)

Rút gọn biểu thức \(B.\)
A.\(B = \frac{{\sqrt x }}{{\sqrt x + 3}}\)
B.\(B = \frac{{ - \sqrt x }}{{\sqrt x + 3}}\)
C.\(B = \frac{{\sqrt x }}{{\sqrt x - 3}}\)
D.\(B = \frac{{\sqrt x }}{{x - 9}}\)

Giải các phương trình sau:
\(a)\,\,\,{x^2} - 5x + 4 = 0 \)
\(b)\,\,{x^4} + {x^2} - 6 = 0\)
A.\(\begin{array}{l}a)\,\,S = \left\{ { - 1;\,\,4} \right\}.\\b)\,\,S = \left\{ { - 2;\,\,2} \right\}.\end{array}\)
B.\(\begin{array}{l}a)\,\,S = \left\{ {1;\,\,4} \right\}.\\b)\,\,S = \left\{ { - \sqrt 2 ;\,\,\sqrt 2 } \right\}.\end{array}\)
C.\(\begin{array}{l}a)\,\,S = \left\{ {1;\,\, - 4} \right\}.\\b)\,\,S = \left\{ { - 2;\,\,2} \right\}.\end{array}\)
D.\(\begin{array}{l}a)\,\,S = \left\{ { - 1;\,\, - 4} \right\}.\\b)\,\,S = \left\{ { - \sqrt 2 ;\,\,\sqrt 2 } \right\}.\end{array}\)

Giải phương trình: (cos2x - sinx - 1) tan(x - ) tan(x + ) = 1 (x ∈ R)
A.x = - + k2π; x = - - k2π, k∈Z
B.x = - + k2π; x = + k2π, k∈Z
C.x = + k2π; x = + kπ, k∈Z
D.x = - k2π; x = + k2π, k∈Z

\( - 17 \le x \le 18\)
A.\(18\)
B.\(20\)
C.\(25\)
D.\(26\)

\( - 17 \le x \le 18\)
A.\(18\)
B.\(20\)
C.\(25\)
D.\(26\)

\( - \left( {x + 84} \right) + 213 = - 16\)
A.\(-145\)
B.\(145\)
C.\(-125\)
D.\(125\)

\(43 + \left( {9 - 21} \right) = 317 - \left( {x + 317} \right)\)
A.\(-31\)
B.\(31\)
C.\(21\)
D.\(-21\)

\(\left( {15 - x} \right) + \left( {x - 12} \right) = 7 - \left( { - 5 + x} \right)\)
A.\(9\)
B.\(10\)
C.\(7\)
D.\(12\)