Nubric answer validation settings

Reference for the available assertions and the properties they check, with examples illustrating each requirement.

Summary

Nubric provides validation rules, called assertions, that enforce specific mathematical properties on a student's answer. They do not check the numerical value of the answer, but its mathematical form. Each assertion evaluates whether the expression satisfies a given property and returns a boolean result.

An answer is considered correct only if it matches the expected value and satisfies all configured assertions.

Location

• Nubric question editor → Answers section → Edit (Evaluation options)

Availability

• Nubric

Default

• No format constraints applied.

Assertions

Simplified

Checks whether the expression cannot be simplified: The numerators and denominators of all quotients must be coprime, as well as roots and powers. There cannot be products of the same variable, there cannot be sums of integers or proportional monomials, fractions must be simplified, etc.

Expanded

Checks whether the expression is in its fully expanded form. A polynomial must be expressed in the standard basis; there cannot be operations between numbers, a sum cannot appear inside a power or a product, etc.

Factorized

Checks whether an integer or a polynomial is factorized: all the factors of the expression must be prime or units. In the polynomial case, the factorization is checked over the ring of polynomials with real coefficients.

Common factor

Checks whether the summands of the answer have no common factors.

Rationalized

Checks whether the expression does not have square (or higher) roots in the denominator. It also checks whether the expression has a pure real denominator (for complex numbers).

Minimal radicands

Checks whether any present radicands are minimal. In particular, it checks whether the integers or polynomials with roots or fractional exponents have no factors that can go outside the radical sign. Can be combined with simplified and/or rationalized assertions in order to check that an expression involving radicals is properly simplified.

Common denominator

Checks whether the answer has a single common denominator in the root of the expression tree, except possibly the sign. When non-algebraic functions are involved, it checks whether the whole expression, as well as the arguments of these functions, have this property.

Behavior

What happens when enabled

An answer is considered correct only if:

1. It matches the expected value.
2. It satisfies all configured assertions.

What happens when disabled

• Disabled assertions do not impose their mathematical form requirements on the student's answer.

Limits

• Assertions check mathematical form. The answer must also match the expected value.

Examples

Simplified

• Numbers

• Polynomials and rational functions

• Roots

• Functions

Expanded

• Numbers

• Polynomials

• Units

Factorized

• Integers

• Polynomials

Common factor

• Numbers

• Polynomials

Rationalized

Minimal radicands

Common denominator

• Rational functions

• Non-algebraic functions

Notes

• Assertions operate on the mathematical meaning of expressions, not their textual representation
• Multiple assertions can be combined
• Assertions are independent of answer correctness

Related articles

• Nubric evaluation options.
• Require simplified answers in a fraction addition question.