Misalkan x1 dan x2 akar akar dari persamaan kuadrat 6x'2-48x+90=0 ,maka (x1-x2)'2

(x1-x2)^2= x1^2 +x2^2-2x1x2
(x1-x2)^2= (x1 + x2)^2 - 4x1x2
= (48/6)^2 -4(90/6)
=8^2 -4(15)
=64-60
4