解方程;1 (x+2y=3,x^2-2y+3x-2=0) 2 ( x^2+y^2=4,2xy=-21)

解方程;1 (x+2y=3,x^2-2y+3x-2=0) 2 ( x^2+y^2=4,2xy=-21)
解方程;1 (x+2y=3,x^2-2y+3x-2=0) 2 ( x^2+y^2=4,2xy=-21)

解方程;1 (x+2y=3,x^2-2y+3x-2=0) 2 ( x^2+y^2=4,2xy=-21)
2y=x-3
x^2-2y+3x-2=0
x^2-x+3+3x-2=0
x^2+2x+1=0
(x-1)^2=0
x=1
x^2+y^2-2xy=4+21=25
(x-y)^2=5
x-y=5 或x-y=-5
x=y+5
2(y+5)y=-21
y^2+10y+21=0
(y-3)(y-7)=0
y1=-3 x1=2
y2=-7 x2=-2
x=y-5
2(y-5)y=-21
y^2-10y+21=0
(y-3)(y-7)=0
y3=3 x3=8
y4=7 x4=12