Checking the first value for negitive

I want students to write an equation in standard form. When they write it, standard form cannot have a negative coefficient with the x value in front. I normally use the evaluate code to compare entries with what is expected, but it wouldn’t catch if a number was negative because it wouldn’t effect the evaluation. Is there a way to assess if the front coefficient is negative so that I can send a warning message to students to make it positive?

Well if Ax+By=C, then -Ax-By=-C. So, you could parseEquation and check if the rhs (right hand side) evaluates to C. Or is it a specific equation?

Solid point, and easy enough to do. Thanks!