Explicație pas cu pas:
.............................
[tex]\it b-a=2\sqrt5+3\sqrt2-2\sqrt5+3\sqrt2=6\sqrt2\\ \\ a\cdotb=(2\sqrt5+3\sqrt2)(2\sqrt5+3\sqrt2)=(2\sqrt5)^2-(3\sqrt2)^2=20-18=2\\ \\ \dfrac{1}{a}-\dfrac{1}{b}=\dfrac{b-a}{ab}=\dfrac{6\sqrt2}{2}=3\sqrt2[/tex]
