So choose one

2. Simplify (√x+√y)? +(√x-√y)？ =2x+2y

3. Calculate √9-4√ 1/2+√8.

=3-2√+4√2

=3+2√2

4、a？ b-b？ a=ab(a-b)

=(3+2√2)(3-2√2)(3+2√2-3+2√2)

=(9-8)4√2

=4√2

Step 5 simplify

Original formula =a+2√a-a

=2√a

6、x？ -2xy+y？

=(x-y)？

=(√7+√5)/2-(√7-√5)/2?

=7