The evaluation type eval lin eqs is used to check if the system of linear equations in the Definition field has the same solution(s) as the system of linear equations in the student’s answer. This works for systems with one, zero, or infinite solutions.

The evaluation type fb lin eqs is used to give predefined feedback on a system of linear equations.

The system does not give an error when the student’s answer is not a system of linear equations. To check this, fb lin eqs can be used.

**Evaluation type: eval lin eqs**

In the Definition field, write the equations in disjunctive normal form with at the end a semicolon and a list of the variables you used separated by commas.

For example, for the system

You should write `(y=x+4) and (y=2-x) ; [x,y] `

in the definition field.

Example 1 (system with one solution):

Example 2 (system with no solutions):

The symbol for the logical AND can be found on the virtual keyboard:

❗ Note that this evaluation type does not have automated feedback.

**Evaluation type: fb lin eqs**

This evaluation type can only be used in (positive and negative) feedback when a solution rule is defined that uses eval lin eqs. It gives feedback on one of the seven cases specified below.

To select a case, type the number of the case (e.g. `1`

) or the name of the case (e.g. `nonlinear`

) in the Definition field. Every case supports automated feedback, and this automated feedback is shown in the examples below. The solution rule that is used is:

1 (nonlinear)

Hits if the student’s answer contains a nonlinear equation.

2 (toobig)

Hits if the solution set of the student’s answer is bigger than the solution set of the Solution, i.e. every solution of the Solution occurs in the student’s answer, but at least one solution of the student’s answer is not a solution of the original system.

3 (toosmall)

Hits if the solution set of the student’s answer is smaller than the solution set of the Solution, i.e. every solution of the student’s answer is correct, but at least one solution of the Solution does not appear in the student’s answer.

4 (incomparable)

5 (strangevar)

Hits if the student’s answer contains a variable that was not defined in the variables list in the Solution.

6 (noequation)

Hits if at least one of the expressions separated by logic symbols in the student’s answer is not an equation.

7 (andornestingtoodeep)

Hits when the AND and OR symbols are used in a way such that the system can’t compare the student’s answer to the solution.