If m and n are the roots of x^2+mx+n=0, m≠0, n≠0, then the sum of the roots is:

1968 AMC 12 Problem 13

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13.

m

and

n

are the roots of

x^2+mx+n=0,

m\ne0,

n\ne0,

then the sum of the roots is:

-\dfrac12

-1

\dfrac12

1

undetermined

Use both the sum and product forms of Vieta’s formulas

The product equation and

n\ne0

determine

m

Because the roots are

m,

n,

Vieta gives

m+n=-m

and

mn=n.

Since

n\ne0,

the second equation gives

m=1,

and then

n=-2.

Their sum is

-1.

Therefore, the correct answer is B.