－4x²－9y²－4x＋12y－1
=-(4x²+9y²+4x-12y+1)
=-[(4x²+4x+1)+(9y²-12y)]
=-[(2x+1)²+(9y²-12y+4-4)]
=-[(2x+1)²+(3y-2)²-4]
=-[(2x+1)²+(3y-2)²]+4
当2x+1=0 3y-2=0时,有最大值,最大值是4.
即x=-1/2 y=2/3