2x(x-1)+4=2x²-2x+4,(ax²-2x+3)-(x²-bx-c)=ax²-2x+3-x²+bx+c=(a-1)x²-(2-b)x+(3+c),
∴a-1=2,a=3;-(2-b)=-2,b=0;3+c=4,c=1.
a-b+c=3-0+1=4
2x(x-1)+4=2x²-2x+4,(ax²-2x+3)-(x²-bx-c)=ax²-2x+3-x²+bx+c=(a-1)x²-(2-b)x+(3+c),
∴a-1=2,a=3;-(2-b)=-2,b=0;3+c=4,c=1.
a-b+c=3-0+1=4