[tex]\it b=\sqrt{\dfrac{36}{25}}+\sqrt{0,64}+\sqrt{1,44}+2\cdot\sqrt{3,61}=\dfrac{6}{5}+0,8+1,2+2\cdot1,9=\\ \\ =1,2+0,8+1,2+3,8=7\in\mathbb{N}[/tex]
