I've set the variables to be v, v', t and c:

Context("ImplicitEquation");

Context()->variables->{namePattern} = qr/[a-z][a-z0-9_]*'*/i;

Context()->variables->are( v => "Real", t => "Real", c => "Real", "v'" => "Real" );

And I'm attempting to get students to enter the following DE:

$de = ImplicitEquation("20*v' = 196 - 4*v");

WeBWorK claims "Can't find any solutions to your equation" when a solution is entered, so I changed the above line to:

$de = ImplicitEquation("20*v' = 196 - 4*v",

solutions => [[49,0],[4,9],[9,8],[14,7],[19,6],[24,5],[29,4]],

tolerance => .001);

But I'm getting the same error still, and I'm unclear (since there are 4 variables in this context) how I should format my specified solutions... I've tried using 4 coordinates in alphabetical order, 2 coordinates: v & v' in both orders, to no avail.

Can anyone offer some guidance?