One-dimensional quadratic equation formula: ax? +bx+c=0 (a≠0, a b c is constant) Discriminant δ = b? The formula for finding the root of -4ac is x=(-b plus or minus √b? -4ac)/2a，(b？ -4ac is not equal to 0).

Vieta's theorem is x 1+x2=-b/a, x1* x2 = c/a.

Virus transmission formula:1+x+x (1+x) = a.

Bifurcation formula: one branch can grow x branches, the second round has x * x = x 2 branches, the third round has x 2 * x = x 3 branches, and so on, the nth theory (n is a positive integer) has x n branches.

The formula of handshaking problem: 1/2x(x- 1)=a The relationship between roots and coefficients of the quadratic equation of one variable, the quadratic equation of one variable, AX 2+BX+C = 0 (A ≠ 0 and △ = B 2-4ac ≥ 0), vieta two roots be X655.

It is proved that if x 1 and x2 are two solutions of the unary quadratic equation ax 2+bx+c = 0, then there are: a (x-x1) (x-x2) = 0 ∴ ax 2-a (x1+x2.