计算9(x+y)2-4(x-y)2怎么做

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计算9(x+y)2-4(x-y)2怎么做

计算9(x+y)2-4(x-y)2怎么做
计算9(x+y)2-4(x-y)2怎么做

计算9(x+y)2-4(x-y)2怎么做
9(x+y)2-4(x-y)2
=(3(x+y))² -(2(x-y))²
=(3x+3y-2x+2y)(3x+3y+2x-2y)
=(x+5y)(5x+y)
=5x²+26xy+5y²

9(x+y)^2-4(x-y)^2
=[3(x+y)-2(x-y)][3(x+y)+2(x-y)]
=[3x+3y-2x+2y][3x+3y+2x-2y]
=(x+5y)(5x+y)

9(x+y)^2-4(x-y)^2
=9(x^2+2xy+y^2)-4(x^2-2xy+y^2)
=9x^2+18xy+9y^2-4x^2+8xy-4y^2
=5x^2+26xy+5y^2

9(x+y)2-4(x-y)2
=(3(x+y)+2(x-y))(3(x+y)-2(x-y))
=(5x+y)(x+5y)