y=-2x²+5x+8=-2(x²+5x/2)+8=-2(x²+5x/2+25/16)+8+25/8=-2(x+5/4)²+89/8y=-3x²+8x-2=-3(x²+8x/3)-2=-3(x²+8x/3+16/9)-2+16/3=-3(x+4/3)²+10/3