用两种方法解方程组2x-y=6,x^2-5xy+6y^2=0
1个回答
2014-01-02
展开全部
①
x^2-5xy+6y^2=0
(x-2y)(x-3y)=0
(1)
x=2y,带入2x-y=6,得
y=2,x=4
(2)
x=3y,带入2x-y=6,得
y=6/5,x=18/5
②
y=2x-6带入x^2-5xy+6y^2=0,得
x�0�5-5x(2x-6)+6(2x-6)�0�5=0
x�0�5-10x�0�5+30x+6(4x�0�5-24x+36)=0
-9x�0�5+30x+24x�0�5-144x+216=0
15x�0�5-114x+216=0
5x�0�5-38x+72=0
(5x-18)(x-4)=0
x1=18/5,x2=4
y1=6/5, y2=2
x^2-5xy+6y^2=0
(x-2y)(x-3y)=0
(1)
x=2y,带入2x-y=6,得
y=2,x=4
(2)
x=3y,带入2x-y=6,得
y=6/5,x=18/5
②
y=2x-6带入x^2-5xy+6y^2=0,得
x�0�5-5x(2x-6)+6(2x-6)�0�5=0
x�0�5-10x�0�5+30x+6(4x�0�5-24x+36)=0
-9x�0�5+30x+24x�0�5-144x+216=0
15x�0�5-114x+216=0
5x�0�5-38x+72=0
(5x-18)(x-4)=0
x1=18/5,x2=4
y1=6/5, y2=2
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