= a(x？ 0? 5 + bx/a + c/a)

= a [ x？ 0? 5 -(- b/a)x + c/a ]

∵ x 1+ x2 = -b/a, x 1x2 = c/a (this is the vietta theorem).

∴ The above formula = a [x? 0? 5 -(x 1+x2)x + x 1x2 ]

= a(x-x 1)(x-x2)

This is the intersection point and can be interchanged with the general formula.