6xy-x²-9y²=-(x²-6xy+9y²)=-(x-3y)²
-m³﹢2m²﹣m=-m(m²-2m+1)=-m(m-1)²
3x²﹣6x﹢3=3(x²-2x+1)=3(x-1)²
x²﹣6x﹙y﹣z﹚﹢9﹙y﹣z﹚²=[x-3(y-z)]²=(x-3y+3z)²
﹙a﹢b﹚²﹣4﹙a﹢b﹚c﹢4c²=[(a+b)-2c]²=(a+b-2c)²x²﹣6x﹙y﹣z﹚﹢9﹙y﹣z﹚²=[x-3(y-z)]²=(x-3y+3z)²這個(gè)好像不對把沒錯(cuò)的你信吧我看了一下[x-3(y-z)]²三的平方不是九嘛x²﹣6x﹙y﹣z﹚﹢9﹙y﹣z﹚²=[x-3(y-z)]²=(x-3y+3z)²[x-3(y-z)]²把這個(gè)乘開試試：x²-2×3(y-z)+[3(y-z)]²=x²-6(y-z)+9(y-z)²