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Let's say you're working with the following problem: f(x) = 2x/(x2 - 4) When finding the domain of a fractional function, you must exclude all the x-values that make the denominator equal to zero, because you can never divide by zero. So, write the denominator as an equation and set it equal to 0. Here's how you do it:  f(x) = 2x/(x2 - 4) x2 - 4 = 0 (x - 2 )(x + 2) = 0 x ≠ (2, - 2) Here's how you do it: x = all real numbers except 2 and -2
Write the problem. Set the denominator equal to zero for fractions with a variable in the denominator. State the domain.