[tex]\displaystyle\bf\\\\Folosim~formula:\\\\(a-b)(a+b)=a^2-b^2\\\\Rezolvare:\\\\(2\sqrt{3}-\sqrt{5})(2\sqrt{3}+\sqrt{5})=\Big(2\sqrt{3}\Big)^2-\Big(\sqrt{5}\Big)^2 =4\times3-5=12-5=\boxed{\bf7\in N}[/tex]
Răspuns:
- 13
Explicație pas cu pas:
(2√3 - √5)(2√3 + √5) =
4 × 3 - 25 =
12 - 25 =
(a - b)(a + b) = a² - b²
