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方程组x+2y=-1 (x)平方+4xy+3(y)平方+2x-y=3
人气:264 ℃ 时间:2019-11-10 14:11:29
解答
x+2y=-1…………………………①
x²+4xy+3y²+2x-y=3
(x+y)(x+3y)+(2x+4y)-5y=3
(x+2y-y)(x+2y+y)+2(x+2y)-5y=3
(-1-y)(-1+y)+2×(-1)-5y=3
(-1)²-y²-2-5y-3=0
1-y²-5y-5=0
y²+5y+4=0………………………②
①②联立解得
(x,y)=(7,-4)(1,-1)
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