a) $\dfrac{3}{5} - \dfrac{2}{5}\cdot x = - 0,5$
⇔ $\dfrac{3 - 2x}{5} = -0,5$
⇔ $3 - 2x = -0,5 . 5 = -2.5$
⇔$- 2x = - 2,5 - 3 = -5,5$
⇔ $x = \dfrac{5,5}{2} = \dfrac{11}{4}$
b) $P = \sqrt{14 + 6\sqrt{5}} + \sqrt{14 - 6\sqrt{5}}$
$= \sqrt{3^{2} + 2.3.\sqrt{5} + (\sqrt{5})^{2}} + \sqrt{3^{2} - 2.3.\sqrt{5} + (\sqrt{5})^{2}}$
$= \sqrt{(3 + \sqrt{5})^{2}} + \sqrt{(3 - \sqrt{5})^{2}}$
$= 3 + \sqrt{5} + 3 - \sqrt{5}$
$= 6$
