a^2+1/4b^2=ab
a^2-ab+1/4b^2=0
当b等于0时,a/b无意义.
当b不等于0时,b^2不等于0,
则等式两边同时除以b^2
得(a^2/b^2)-(a/b)+1/4=0
(a/b)^2-(a/b)+1/4=0
设x=a/b
则x^2-x+1/4=0
(x-1/2)^2=0
则a/b=x=1/2