8x^2-4x+5=0
8(x^2-1/2x)+5=0
8(x^2-1/2x+1/16-1/16)+5=0
8(x^2-1/2x+1/16)-1/2+5=0
8(x-1/4)^2+9/2=0
(x-1/4)^2=-9/16
x-1/4=3/4i,或x-1/4=-3/4i
x=3/4i+1/4,或x=1/4-3/4i
8x^2-4x+5=0
8(x^2-1/2x)+5=0
8(x^2-1/2x+1/16-1/16)+5=0
8(x^2-1/2x+1/16)-1/2+5=0
8(x-1/4)^2+9/2=0
(x-1/4)^2=-9/16
x-1/4=3/4i,或x-1/4=-3/4i
x=3/4i+1/4,或x=1/4-3/4i