Ai giải minh với ạ a). √2+√18-√50 b). 2\√5+2 +2\√5-2

$a)$ $\sqrt{2}+$$\sqrt{18}-$ $\sqrt{50}$

$=$ $\sqrt{2}+ $ $\sqrt{9.2}- $ $\sqrt{25.2}$ 

$=$$\sqrt{2}+$ $3\sqrt{2}- $ $5\sqrt{2}$ 

$=$ $-\sqrt{2}$

b) $\frac{2}{\sqrt{5}+2}$ $+$ $\frac{2}{\sqrt{5}-2}$

$=$ $\frac{2.(\sqrt{5}-2)+ 2.(\sqrt{5}+2)}{(\sqrt{5}+2)(\sqrt{5}-2)}$ 

$=$ $\frac{2\sqrt{5}-4+2\sqrt{5}+4}{5-4}$ 

$=$ $4√5$

`a)`

`sqrt2+sqrt18-sqrt50`

`=sqrt2+sqrt(9.2)-sqrt(25.2)`

`=sqrt2+3sqrt2-5sqrt2`

`=-sqrt2`

`b)`

`2/(sqrt5+2)+2/(sqrt5-2)`

`=(2(sqrt5-2))/((sqrt5+2)(sqrt5-2))+(2(sqrt5+2))/((sqrt5+2)(sqrt5-2))`

`=(2sqrt5-4)/(5-4)+(2sqrt5+4)/(5-4)`

`=2sqrt5-4+2sqrt5+4`

`=4sqrt5`