因式分解 3x²+4xy-y²
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因式分解 3x²+4xy-y²
![因式分解 3x²+4xy-y²](/uploads/image/z/19895707-19-7.jpg?t=%E5%9B%A0%E5%BC%8F%E5%88%86%E8%A7%A3+3x%26sup2%3B%2B4xy-y%26sup2%3B)
方法一
=7x²-(4x²-4xy+y²)
=7x²-(2x-y)²
=(√7x+2x-y)(√7x-2x+y)
方法二
=3(x²+4xy/3+4y²/9-7y²/9)
=3[(x+2y/3)²-7y²/9]
=3(x+2y/3+√7y/3)(x+2y/3-√7y/3)
=7x²-(4x²-4xy+y²)
=7x²-(2x-y)²
=(√7x+2x-y)(√7x-2x+y)
方法二
=3(x²+4xy/3+4y²/9-7y²/9)
=3[(x+2y/3)²-7y²/9]
=3(x+2y/3+√7y/3)(x+2y/3-√7y/3)