中2數,因式分解一條 (20分)

(2x+1)(x-y)-(3x+1)(x-y)
=(x-y)(2x+1-3x-1)
=(x-y)(-x)
=-x(x-y)

上面好多個人都做錯數呀 題目話因式分解呀 唔係展開呀

(2x+1)(x-y)-(3x+1)(x-y)<--當中(x-y)係(2x+1)(x-y)&(3x+1)(x-y)都有既項
所以就要抽(x-y)出黎
如下
(2x+1)(x-y)-(3x+1)(x-y)
=(x-y)((2x+1)-(3x+1))
=(x-y)(2x+1-3x-1)
=(x-y)(-x)<--去左咁既樣呢,就要展開啦p.s(x-y)(單一個數)
=y-x

如果你仲係唔明既話,就將x-y當係a咁睇
設x-y為a
(2x+1)(x-y)-(3x+1)(x-y)
=(2x+1)a-(3x+1)a
=a((2x+1)-(3x+1))
=a(2x+1-3x-1)
=a(-x)<--而家先將(x-y)代返入去a都得,方便你計就得

仲係唔識就聯絡我啦
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(2x+1)(x-y)-(3x+1)(x-y)
=(x-y)(2x+1-3x-1)
=(x-y)(-x)
=-x(x-y)
=-x^2+xy

(2x+1)(x-y)-(3x+1)(x-y)
= 2x*-y-3x*+y
= -x*

注意: *=2

# 首先, 將2x乘x, =2x* (x乘x=x*), 接著1乘-y=-y.
同道理, -3x乘x=-3x*, -1乘-y=y.接下來你應該識La!

(2x+1)(x-y)-(3x+1)(x-y)
2 2
=2x +X-2xy-y-3x +x+3xy-y
2
=-x +2x+xy-2y



最詳細既步驟!!!!!!!!

(2x+1)(x-y)-(3x+1)(x-y)
=(x-y)[(2x+1)-(3x+1)]
=(x-y)(2x+1-3x-1)
=(x-y)(-x)
=-x^2+xy