WeBWorK Problems

General Solution - Vector Parametric Equation

General Solution - Vector Parametric Equation

by Marie-Claude Bonneau -
Number of replies: 2

Hello,

I wanted to make sure students could enter the general solution of a system of linear equations as a vector form without the actual standard vector format. So, I modified the following problem  /Library/Rochester/setLinearAlgebra1Systems/ur_la_1_14.pg  using https://webwork.maa.org/wiki/VectorParametricLines as a guide. The problem is that WeBWorK recognizes (21,-14,t)+t(22,-17,0) as equivalent to (21,−14,0)+t(22,−17,1)

Is there a way of having WeBWorK recognize that (21,-14,t)+t(22,-17,0) is incorrect?

Enclosed is the relevant portion of the modified code.

Thank you.

Marie-Claude

In reply to Marie-Claude Bonneau

Re: General Solution - Vector Parametric Equation

by Danny Glin -
It is by design that WeBWorK recognizes (21,-14,t)+t(22,-17,0) as correct, since it is mathematically equivalent to (21,−14,0)+t(22,−17,1). The goal with WeBWorK answer checkers is to accept any correct answer.

I think that it will be very hard to write an answer checker that accepts (21,−14,0)+t(22,−17,1) but not (21,-14,t)+t(22,-17,0). If you want to force the students to enter an answer in a specific format, you would need to write heuristics that determine what is acceptable. For example, should t(22,−17,1)+(21,-14,0) be marked correct? In fact, the original question you quoted does a good job of forcing the student to separate the constant, and it also allows for different parameterizations, so I'm not sure what you are trying to accomplish.
In reply to Danny Glin

Re: General Solution - Vector Parametric Equation

by Marie-Claude Bonneau -

Thank you Danny. I wanted students to enter their answer just like they would on a test, without prior knowledge of the number of free variables.