Find all numbers that must be excluded from the domain of the given rational expression.

Question

1) x^2+4x/x^2-16

2) 6x^3y-6xy/x^3+5x^2+4x

3) 4-x^2/x^2+x-6

Answer 1

look at the denominators.

a. (x-4)(x+4)
b. x(x+5)(x+1)
c. (x+3)(x-2)

now I ask you: what values of x in each of these will make the product zero?