y^2-7y-(x+3)(x-4)
=y^2-7y+49/4-49/4-(x^2-x+1/4-1/4-12)
=(y-7/2)^2-(x-1/2)^2-49/4+1/4+12
=(y-7/2)^2-(x-1/2)^2
=[(y-7/2)+(x-1/2)]×[[(y-7/2)-(x-1/2)]
=(x+y-4)×(y-x-3)
思路是：将y与X分别凑成完全平方的形式,然后再利用平方差公式展开整理就可得到.
每一步骤都很详细,
因式分解：y^2-7y-(x+3)(x-4)
y^2-7y-(x+3)(x-4)
=y^2-7y+49/4-49/4-(x^2-x+1/4-1/4-12)
=(y-7/2)^2-(x-1/2)^2-49/4+1/4+12
=(y-7/2)^2-(x-1/2)^2
=[(y-7/2)+(x-1/2)]×[[(y-7/2)-(x-1/2)]
=(x+y-4)×(y-x-3)
思路是：将y与X分别凑成完全平方的形式,然后再利用平方差公式展开整理就可得到.
每一步骤都很详细,