3x平方-5x+1=0
x=[5±√(5^2-4*3*1)]/(2*3)
=(5±√13)/6
2x平方+根号3x-9=0
x={-√3±√[(√3)^2+4*2*9]}/(2*2)
={-√3±√75}/4
=(-√3±5√3)/4
x1=-3√3/2
x2=√3