Create a new question type: EQUATIONS
This is similar to another post about expanding the symbols allowed in the "Expression" types of questions.
Sometimes answers ARE equations, thus the = sign is required.
Also, interval notation, such as (a,b) or (-infinity, infinity) are needed either in the existing "EXPRESSION" question types or this new "EQUATION" question types. Note: the words "infinity" above would be substituted with the infinity symbol, which would need to be made available.