I have written a question where I ask students to solve a quadratic inequality. In the picture below you will all variables which I define, and how the input form is set up.

In general, the roots might have the form "-(x+sqrt( y ))/z" (for certain numbers x,y,z). These are given by "res3" and/or "res4" in the picture.

If I only ask them to input these roots as answers, all the usual variations work: "-(x+sqrt( y ))/z", or "(-x-sqrt( y )/z", or "(x+sqrt( y ))/(-z)".

However, in res5 I ask them to input the interval solution of the quadratic, and some of these are not accepted. In my last try, only "-(x+sqrt( y ))/z" and "(x+sqrt( y ))/(-z)" were accepted, but not "(-x-sqrt( y ))/z".

I really have no idea what is wrong, and any help is deeply appreciated.