a quadratic equation of one unknown (english name: quadratic equation of one unknown) refers to an integral equation that contains only one unknown, and the highest degree of the unknown is quadratic. the general form of this equation is: ax²+bx+c=0 (a≠ 0), where ax² is a quadratic term, bx is a linear term, c is a constant term, and a and b are constants. a≠0 is an important condition, otherwise there is no guarantee that the highest degree of unknowns in the equation is quadratic.

when δ=b^2-4ac≥0, x=[-b±(b^2-4ac)^(1/2)]/2a

when δ=b^2-4ac<0, x={-b±[(4ac-b^2)^(1/2)]i}/2a (i is the imaginary unit)

how to combine quadratic equations of one variable:

ax^2+bx+c=0 (a, b, c are constants)

x^2+bx/a+c/a=0

(x+b/2a)^2=(b^2-4ac)/4a^2

x+b/2a=±(b^2-4ac)^(1/2)/2a

x=[-b±(b^2-4ac)^(1/2)]/2a