Question 6289
the illegal values is the values that make the two denominators equal to zero.

c^2+5c-14=0
c^2-2c-15=0

Solve both:

*[invoke quadratic "c", 1, 5, -14]
*[invoke quadratic "c", 1, -2, -15]

So, the illegal values are 2, -7, 5, -3, you are right. Good job!