-x²-10x-23=-(x²+10x+23)=-((x²+2*x*5+25)-2)=-((x+5)²-2)=-(x+5)²+2
-4x²+12x-4=-(4x²-12x+4)=-((2x)²-2*2x*3+9)-5)=-((2x-3)²-5)=-(2x-3)²+5
-x²-10x-23=-(x²+10x+23)=-((x²+2*x*5+25)-2)=-((x+5)²-2)=-(x+5)²+2
-4x²+12x-4=-(4x²-12x+4)=-((2x)²-2*2x*3+9)-5)=-((2x-3)²-5)=-(2x-3)²+5