Quadratic equations and inequalities

9000034906

Level: 
B
The solution set of one of the following quadratic inequalities is \(\left (-\infty ;-\frac{3} {5}\right )\cup \left (\frac{1} {6};\infty \right )\). Determine this inequality.
\(\left (5x + 3\right )\left (1 - 6x\right ) < 0\)
\(\left (5x - 3\right )\left (6x + 1\right ) < 0\)
\(\left (5x + 3\right )\left (1 - 6x\right ) > 0\)
\(\left (5x - 3\right )\left (6x + 1\right ) > 0\)

9000034907

Level: 
B
Find all \(x\in \mathbb{R}\) for which the following expression takes nonnegative values. \[ -2\left (x - 3\right )\left (2 - x\right ) \]
\(\left (-\infty ;2\right ] \cup \left [ 3;\infty \right )\)
\(\left [ 2;3\right ] \)
\(\left (2;3\right )\)
\(\left (-\infty ;2\right )\cup \left (3;\infty \right )\)

9000034908

Level: 
B
Find all \(x\in \mathbb{R}\) for which the following expression is nonpositive. \[ \left (x + 1\right )\left (4 + x\right ) \]
\(\left [ -4;-1\right ] \)
\(\left (-\infty ;-4\right ] \cup \left [ -1;\infty \right )\)
\(\left (-4;-1\right )\)
\(\left (-\infty ;-4\right )\cup \left (-1;\infty \right )\)

9000034905

Level: 
B
The solution set of one of the following quadratic inequalities is the interval \(\left [ -\frac{7} {6}; \frac{3} {4}\right ] \). Determine this inequality.
\(\left (x + \frac{7} {6}\right )\left (x -\frac{3} {4}\right )\leq 0\)
\(\left (x + \frac{7} {6}\right )\left (x -\frac{3} {4}\right )\geq 0\)
\(\left (x -\frac{7} {6}\right )\left (x + \frac{3} {4}\right )\geq 0\)
\(\left (x -\frac{7} {6}\right )\left (x + \frac{3} {4}\right )\leq 0\)

9000033708

Level: 
C
A stone has been thrown vertically up at the velocity \(15\, \mathrm{m}\, \mathrm{s}^{-1}\) from the initial height \(10\, \mathrm{m}\). How long (in seconds) has been the height of the stone at least \(20\, \mathrm{m}\)? Hint: The height \(h\) is given by the expression \(h = s_{0} + v_{0}t -\frac{1} {2}gt^{2}\), the standard acceleration is \(g\mathop{\mathop{\doteq }}\nolimits 10\, \mathrm{m}\, \mathrm{s}^{-2}\).
exactly \(1\, \mathrm{s}\)
less than \(1\, \mathrm{s}\)
more than \(1\, \mathrm{s}\)
The information is not sufficient to give a definite answer.

9000033709

Level: 
C
A square shaped garden with the side \(a\) should be reduced by a length \(x\) to another square garden. The difference between the areas of the gardens should not be bigger than \(25\%\) of the original area. Find the possible values of \(x\).
\(x\leq a -\frac{\sqrt{3}} {2} a\)
\(x\leq \sqrt{3}a\)
\(x\leq \frac{3} {4}a\)
\(x\leq a + \frac{\sqrt{3}} {2} a\)