a(x-1)=2x
ax-a=2x
(a-2)x=a
x=a/(a-2)
a²y²+y²=a
(a^2+1)y^2=a
y=±√[a/(a^2+1)]
(x²-x)²-4x²+4x-12=0
(x^2-x)^2-4(x^2-x)+2^2-16=0
[(x^2-x)-2]^2=16
x^2-x-2=±4
则x^2-x-6=0或x^2-x+2=0
x^2-x+2=0无实数解
x^2-x-6=0的解为：x1=3,x2=-2
5(x-a)=ax+b
5x-5a=ax+b
(5-a)x=5a+b
x=(5a+b)/(5-a)