求分解因式题:y^2-9(x+y)^2

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求分解因式题:y^2-9(x+y)^2
求分解因式题:y^2-9(x+y)^2

求分解因式题:y^2-9(x+y)^2
y^2-9(x+y)^2
=y^2-[3(x+y)]^2
=y²-(3x+3y)²
=(y+3x+3y)(y-3x-3y)
=(3x+4y)(﹣3x-2y)
=﹣(3x+4y)(3x+2y)

原式=y²-[3(x+y)]²
=[y+3(x+y)][y-3(x+y)]
=(3x+4y)(-3x-2y)
=-(3x+4y)(3x+2y)

-(3x+4y)(3x+2y)

原式=y²-3²(x+y)²
=y²-[3(x+y)]²
=[y+3(x+y)] × [y-3(x+y)]
=(3x+4y)[-(3x+2y)]
=-(3x+4y)(3x+2y)

公式就是 a²-b²=(a+b)(a-b)
你把题目写成a²-b²套下公式就行了