// minds behind maths
François Viète
1540–1603 · Algebra
François Viète (Latinised as Franciscus Vieta) was a French mathematician and a founder of modern symbolic algebra, introducing the systematic use of letters for both knowns and unknowns. He is best known today for Vieta's formulas, which relate the coefficients of a polynomial to sums and products of its roots. For a quadratic, this is exactly the (x+a)(x+b) = x² + (a+b)x + ab relationship: the middle coefficient is the sum of the roots and the constant is their product — the principle behind the product identities in this section.
Source: Wikipedia — Vieta's formulas
Formulas that trace back to François Viète
(ax+b)(cx+d)
(ax+b)(cx+d) = acx² + (ad+bc)x + bd
(x+a)(x+b)
(x+a)(x+b) = x² + (a+b)x + ab
(x−a)(x−b)
(x-a)(x-b) = x² - (a+b)x + ab