4x²-√5x-1=0
a=4,b=-√5,c=-1
x=[-b±√(b²-4ac)]/2a
=﹛-(-√5)±√[(-√5)²-4×4×(-1)]﹜/(2×4)
=[√5±√(5+16)]/8
=(√5±√21)/8
x1=(√5+√21)/8
x2=(√5-√21)/8