I am having trouble using the quadratic equation as a calculated question type using dragmath on moodle 1.9.10. I finally managed to get the equation in using:

x= \frac{-\left(b\right) \pm \sqrt{b^{2}-4 \cdot ac} }{2 \cdot a}

But using the calculated question text:

{a}x^{2} + {b}x + {c}

to generate 3 variables then using the answer key:

(-1*{b}+sqrt(({b}^2)-(4*{a}*{c})))/2*{a})

The answer equation is not accepted, how do I make it work? I know I am using the positive value only but this is due to simplicity I am asking for the "maximum value of x" in the question text. I am planning on setting the range of {a} to 1-10 and {c} to 0-10 so that the condition 4ac will at most = 400 and setting {b} to a range of 21-100 will ensure a positive square root is always produced.

What am I missing here to make the answer formula work?