x²+2x-3=x²+2x+1-4=（x+1）^2-4=(x+1-2)(x+1+2)=(x-1)(x+3)x²-2x-8=x²-2x+1-9=（x-1）^2-9=(x-1-3)(x-1+3)=(x-4)(x+2)2m²-6m+3=
