计算(x+y-3)(x-y+3)还有(x-2y+3z)^2

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计算(x+y-3)(x-y+3)还有(x-2y+3z)^2

计算(x+y-3)(x-y+3)还有(x-2y+3z)^2
计算(x+y-3)(x-y+3)
还有(x-2y+3z)^2

计算(x+y-3)(x-y+3)还有(x-2y+3z)^2
x^2-(y-3)^2=x^2-y^2+6y-9

x^2-y^2+6y-9

(x+y-3)(x-y+3)
=x的平方-(3-y) 的平方
=x^2-y^2+6y-9

(x+y-3)(x-y+3)=[x+(y-3)][x-(y-3)]=x^2-(y-3)^2=x^2-(y^2-6y+9)

=[x+(y-3)][x-(y-3)]
=x²-(y-3)²
=x²-y²+6y-9

-(x+y-3)的平方

x2-y2+3(2y-3)