1条2元2次方程,写过程.(50分,先30再追加20)
问题描述:
1条2元2次方程,写过程.(50分,先30再追加20)
y=x^2+4
x=y^2+4
答
y=x^2+4 (1)
x=y^2+4(2)
(1)-(2)
y-x=x^2-y^2
x^2-y^2+x-y=0
(x+y)(x-y)+(x-y)=0
(x-y)(x+y+1)=0
x-y=0
x=y 或x+y+1=0.