(x-y+1)²+丨2x+y-7丨=0(x-y+1)²=0丨2x+y-7丨=0x-y+1=02x+y-7=0x-y=-12x+y=73x=6x=2y=x+1=2+1=3x²-3xy+2y²=2²-3*2*3+2*3²=4-18+18=4
