C

The following equation has a double solution $x=1$. Find all solutions. $$x^4+2x^3-3x^2-4x+4=0$$

Find the condition which is equivalent to the fact that the equation $a{x}^2+bx+c=0$ with $x\in \mathbb{R}$ and real coefficients $a$, $b$, $c$ has two solutions and one of the solutions is a reciprocal value of the second solution.

Which part of the plane describes the solution of the following system of inequalities? $$\begin{array}{rlrl}x+\phantom{3}y\le & 3& & \\ y-2x<& -1& & \end{array}$$

Which part of the plane describes the solution of the following system of inequalities? $$\begin{array}{rlrl}2x-y\ge & 2& & \\ 2x+y\ge & -2& & \end{array}$$