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解方程组2x*+2xy+4y*+x=19;x*+xy+2y*-y=9
人气:192 ℃ 时间:2019-09-20 13:03:19
解答
x^2+xy+2y^2=9+y
2x^2+2xy+4y^2=18+2y
2x^2+2xy+4y^2+x=19
18+2y+x=19
x+2y=1
x=1-2y
(1-2y)^2+(1-2y)y+2y^2-y=9
4y^2-4y+1+y-2y^2+2y^2-y-9=0
4y^2-4y-8=0
y^2-y-2=0
(y-2)(y+1)=0
y1=2 y2=-1
x1=-3 x2=3
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