(
)(x) =
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=
×
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The denominator cannot be zero as this would make the rational function undefined. Equating the denominator to zero and solving gives the value that x cannot be
solve 7x + 28 = 0 ⇒ x = - 4 ← excluded value
domain is x ∈ (- ∞, - 4 ) ∪ (- 4, + ∞ )