Question 3
(HUN) Let $x$ be an angle and let the real numbers $a,b,c,\cos x$ satisfy the following equation:
$$a\cos^2x+b\cos x+c=0.$$
Write the analogous quadratic equation for $a,b,c,\cos2x$. Compare the given and the obtained equality for $a=4,b=2,c=-1$.
$$a\cos^2x+b\cos x+c=0.$$
Write the analogous quadratic equation for $a,b,c,\cos2x$. Compare the given and the obtained equality for $a=4,b=2,c=-1$.