Nature of roots from discriminant (D>0: two distinct real; D=0: repeated real; D<0: conjugate non-real)

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D>0: two distinct real; D=0: repeated real; D<0: conjugate non-real (real coeffs)

What each symbol means

SymbolWhat it stands for
DDiscriminant
a,b,cReal coefficients, a≠0

When to use this

ax²+bx+c=0 with real a,b,c and a≠0.