2018 Kosen Maths

QUESTIONS AND SOLUTIONS

 

I.   PART 1

 

QUESTION 01

Solve the equation \(x^3 + x^2 - 4x + 2 = 0\).

 


QUESTION 02

Solve the equation \(\cos 2x + 3 \cos x + 2 = 0 \quad (0 < x < 2 \pi)\).

 


QUESTION 03

Solve the equation \(3^{2x+1} + 5 \:.\: 3^x - 2 = 0\)

 


QUESTION 04

Solve the inequality \(4^{x+1} + 11 \:.\: 2^x - 3 > 0\).

 


QUESTION 05

Solve the equation \((\log_2 x )^2 = \log_4 x^4\).

 


QUESTION 06

Solve the inequality \(\log_3 (3 - x) + \log_3 (x + 1) < 1\).

 


QUESTION 07

Let \(\vec a\) and \(\vec b\) be two vectors such as \(\| a \| = 1, \| b \| = 3\) and \(\vec a \cdot \vec b = 2\). Calculate \(\| 2 \vec a - 3 \vec b \|\).

 


QUESTION 08

The line \(l\) passes through the intersection point of the line \(7x - y = 5\) with the line \(3x + 2y = 7\). The line \(l\) is perpendicular to the line \(x - 2y- 3 = 0\). Find the equation of the line \(l\).

 


QUESTION 09

The Nth partial sum \(S_N\) of the sequence \(\{ a_n \}\) satisfies the following condition:

\(S_N = 3^N + 2N -1\)

Find the nth term \(a_n\) of the sequence \(\{ a_n \}\).

 


QUESTION 10

Calculate \(\displaystyle \lim_{x \rightarrow \sim} \left(\sqrt{x^2 + 3x + 4} - x \right)\).

 


QUESTION 11

Let \(f(x) = \log_e \{x (x + e) \}\). Calculate \(f'(e)\).

 


QUESTION 12

Calculate \(\displaystyle \int_0^{\dfrac {\pi}{2}} x \cos x \: dx\)

 


II.   PART 2

 

Let \(A = \begin{pmatrix} 3 & 2 \\ -1 & 0 \end{pmatrix}\), \(B = \begin{pmatrix} a & -2 \\ 1 & 2 \end{pmatrix}\) dan \(C = \begin{pmatrix} b & 2 \\ -1 & -1 \end{pmatrix}\). satisfying the following condition.

\(B^2 = B\)

\(BC = CB = \begin{pmatrix} 0 & 0 \\ 0 & 0 \end{pmatrix}\)

 

QUESTION 01

Find \(a\) and \(b\).

 


QUESTION 02

Suppose \(A = xB + yC\). Find \(x\) and \(y\).

 


QUESTION 03

Find \(A^5\).

 


III.   PART 3

 

Let \(f(x) = \dfrac {\log_e x}{x} \quad (x > 0)\)

 

QUESTION 01

Find the maximum value \(M\) of \(f(x).

 


QUESTION 02

Find the tangent line \(l\) to the curve \(y = f(x)\) passing through the point \((0,0)\).

 


QUESTION 03

Calculate the area \(S\) among the curve \(y = f(x)\), the line \(l\), and the x-axis.

 


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