What is the target of your problems Daniel ? Beginners ? You must give explanations and examples. Cody is a game, try to be creative. Look at Grant III series about divisors and scrabble to understand what I mean. Otherwise, please stop to create these problems. It's so boring ...

Not to mention, that even if the test suite wasn't broken it does not test for the question asked. I.E. it does not test that the answer is an equation.

c_0 = 1;
t = 10;
Test case needs to be changed. argument x needs to be changed into c_0 and t.