-x²-y²+2x-4y-17=(-x²+2x-1)+(-y²-4y-4)-12=-(x²-2x+1)-(y²+4y+4) -12=-(x-1)²-(y+2)²-12=-[(x-1)²+(y-2)²]-12平方项恒非负,(x-1)²≥0 (y-2)²≥0(x-1)...