1.x²-y²=(x+y)(x-y)=2xy...1
x²-y²-2xy=0
x²-2xy+y²=2y²
(x-y)²=2y².2
2/1=(x-y)/(x+y)=2y²/2xy=1/x
2.x²+xy-2y²=0
x²+3xy-2y²=2xy.1
x²+xy-2y²=0
x²-2y²=-xy.2
1/2=2xy/(-xy)=-2
3.3-x
---
x-2 3-x 3-x 3-2√2
---------- =------ = ----- = -------
2 x²-4-2 x²-6 2
x+2- ——
x-2