(x²+1/2xy+1/2y²)-(x²+2/3xy-2y²),其中x=-1/4,y=1/2
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![(x²+1/2xy+1/2y²)-(x²+2/3xy-2y²),其中x=-1/4,y=1/2](/uploads/image/z/806139-27-9.jpg?t=%EF%BC%88x%26%23178%3B%2B1%2F2xy%2B1%2F2y%26%23178%3B%EF%BC%89-%EF%BC%88x%26%23178%3B%2B2%2F3xy-2y%26%23178%3B%EF%BC%89%2C%E5%85%B6%E4%B8%ADx%3D-1%2F4%2Cy%3D1%2F2)
(x²+1/2xy+1/2y²)-(x²+2/3xy-2y²),其中x=-1/4,y=1/2
(x²+1/2xy+1/2y²)-(x²+2/3xy-2y²),其中x=-1/4,y=1/2
(x²+1/2xy+1/2y²)-(x²+2/3xy-2y²),其中x=-1/4,y=1/2
(x²+1/2xy+1/2y²)-(x²+2/3xy-2y²)
=x²+1/2xy+1/2y²-x²-2/3xy+2y²
=(1-1)x²+(1/2-3/2)xy+(1/2+2)y²
=-xy+5/2y²
=-(-1/4)*1/2+5/2*(1/2)²
=1/8+5/8
=6/8
=3/4