很难的【因式分解】:3x^2+4xy-y^2=3(x-((2+√7)/3)y))(x-((2-√7)/3)y))

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很难的【因式分解】:3x^2+4xy-y^2=3(x-((2+√7)/3)y))(x-((2-√7)/3)y))

很难的【因式分解】:3x^2+4xy-y^2=3(x-((2+√7)/3)y))(x-((2-√7)/3)y))
很难的【因式分解】:3x^2+4xy-y^2
=3(x-((2+√7)/3)y))(x-((2-√7)/3)y))

很难的【因式分解】:3x^2+4xy-y^2=3(x-((2+√7)/3)y))(x-((2-√7)/3)y))
3x^2+4xy-y^2 = 3(x^2+ xy*4/3 - y^2*1/3) = 3[(x^2+ 2*2/3 *xy +4/9y^2) - y^2/3- 4/9y^2] = 3[(x+2/3y)^2 - 7/9 y^2]
=3(x+2/3y +√7/3y)(x+2/3y - √7/3y) = 3[x+(2+√7)/3y][x+(2-√7)/3y]

把y看成已知数
用求根公式求方程3x^2+4xy-y^2=0的解

3x^2+4xy-y^2
=3(x^2+4/3xy-y^2/3)
=3((x^2+4/3xy+4/9y^2)-7/9y^2)
=3((x+2/3y)^2-7/9y^2)
=3(x-((2+√7)/3)y))(x-((2-√7)/3)y))

3x^2+4xy-y^2=0
x为未知,y已知量;公式法求解
x=-(2±√7)y/3
3x^2+4xy-y^2=3(x-((2+√7)/3)y))(x-((2-√7)/3)y))