A is a quadratic coefficient, b is a linear coefficient and c is a constant.

The unary quadratic AX 2+BX+C = 0 can be solved by formula x=, which is a formula that directly represents the root with the coefficient of the equation. This formula was given by Al Khorezmo of Central Asia as early as the 9th century.

Qin, a mathematician in the Southern Song Dynasty, discovered the formula for finding the root of the cubic equation of one yuan at the latest in 1247, which took Europeans more than 400 years to discover, but this formula is still named after that European in China's textbooks. ?

The root formula of unary cubic equation AX 3+BX 2+CX+D = 0 is 1545, which was published by Italian Cardan in his book Algebraic Dafa, and people called it "Cardan Formula". However, in fact, the person who discovered the formula was not Kadan, but Tattaglia N. (about 1499~ 1557).