If α,β\alpha, \betaα,β are zeroes of ax2+bx+cax^2 + bx + cax2+bx+c (a≠0a\ne 0a=0), then α+β=−b/a\alpha + \beta = -b/aα+β=−b/a and αβ=c/a\alpha\beta = c/aαβ=c/a. This lets you construct a quadratic with given zeroes: x2−(α+β)x+αβ=0x^2 - (\alpha+\beta)x + \alpha\beta = 0x2−(α+β)x+αβ=0.