5x²-3xy+1/2y²-2x+1/2y+1/4=0
(9x²-3xy+1/4y²)-4x²-2x+1/4y²+1/2y+1/4=0
（3x-1/2y)²-(4x²+2x+1/4)+1/4+(1/4y²+1/2y+1/4)=0
（3x-1/2y)²-(2x+1/2)²+1/4+(1/2y+1/2)²=0