This is known as quadratic algebra.
To find it, you can use the quadratic formula but that might take a while.
We can factor it out and get
-3(mx² + mx - 1)
We can then set mx² + mx = 1
It would have no solutions
Edit: Above is wrong! I made the mistake of factoring 3 when it cant be factored.
Here is the solution
mx²-3mx=-3
Divide both by -3
mx²+mx=1
And I really messed this up. Its been a long time since quad. Sorry, but I cant seem to get the answer. Try and look up the quadratic formula and see if you can use that