a=0则-x=0
x=0
a≠0
两边除以a
x²-x/a=1
x²-x/a+1/(4a²)=1++1/(4a²)
(x-1/2a)²=(4a²+1)/4a²
x-1/2a=±√(4a²+1)/2a
综上
a=0,x=0
a≠0,x=[1-√(4a²+1)]/2a,x=[1+√(4a²+1)]/2a