If $n$ is a constant and if there exists a unique value of $m$ for which the quadratic equation $x^2 + mx + (m+n) = 0$ has one real solution, then find $n$.

Guest Aug 3, 2020

#1**+5 **

Since this is a monic quadratic, we can use vieta's formula : https://artofproblemsolving.com/wiki/index.php/Vieta%27s_Formulas.

So, we see that mn=n+m, and -m-n=m. Now, here is where is get's a bit tricky. When we add m to both sides of the second equation, we see that -n=2m. Divide by -1, we see that n=-2m.

Here is what I want you do to: plug -2m for n in the first equation, then solve for m.

Then, put that into n=-2m, and solve for n.

Good luck!

:)

ilorty Aug 3, 2020