4x^2+5x-1=0
x^2+5x/4-1/4=0
x^2+5x/4+25/64-25/64-16/64=0
(x+5/8)^2-41/64=0
(x+5/8-√41/8)(x+5/8+√41/8)=0
x=-5/8+√41/8或x=-5/8-√41/8