a(x^2+b/a x+c/a)=0(x+b/2a)^2+c/a-(b/2a)^2=0(x+b/2a)^2=(b^2/4-ac)/a^2x1=[-b+(b^2-4ac)^1/2]/2a,x2=[-b-(b^2-4ac)^1/2]/2a
