← Potenssi · Lukion taulukot · Kokonaislukukertoiminen polynomi →
a x 2 + b x + c = 0 {\displaystyle ax^{2}+bx+c=0}
x = − b ± D 2 a = − b ± b 2 − 4 a c 2 a {\displaystyle x={\frac {-b\pm {\sqrt {D}}}{2a}}={\frac {-b\pm {\sqrt {b^{2}-4ac}}}{2a}}}
Diskriminantti D = b 2 − 4 a c {\displaystyle D=b^{2}-4ac}
D > 0, 2 reaalijuurta
D = 0, 1 reaalijuuri
D < 0, Ei reaalijuuria, imaginaarijuuret − b ± i − D 2 a {\displaystyle {\frac {-b\pm {\mathit {i}}{\sqrt {-D}}}{2a}}}
x 2 + p x + q = 0 {\displaystyle x^{2}+px+q=0}
x = − p 2 ± ( p 2 ) 2 − q {\displaystyle x=-{\frac {p}{2}}\pm {\sqrt {\left({\frac {p}{2}}\right)^{2}-q}}}
x 1 + x 2 = − p {\displaystyle x_{1}+x_{2}=-p}
x 1 x 2 = q {\displaystyle x_{1}x_{2}=q}
