2-8 The rational algebraic function, its domain and simplifying
Point 8 of 11 — Unit 2: The Quadratic, Polynomial and Rational Functions and Their OperationsQuestion bank: 0 questions (0 with pictures)
08 2-8 The rational algebraic function, its domain and simplifying
A rational function is f(x) = P(x)/Q(x), Q ≠ 0, where P and Q are polynomials.
Domain: all reals except the values that make Q(x) = 0. Example: Q(x) = x² − 9 excludes x = ±3, so the domain is ℝ − {−3, 3}.
Simplifying: factor numerator and denominator, cancel only common factors, and keep the excluded values as restrictions. (x² − 1)/(x² + x) = (x − 1)(x + 1)/[x(x + 1)] = (x − 1)/x, x ≠ 0, ±1… restrictions x ≠ 0, x ≠ −1.
Zeros of a rational function: the zeros of the numerator that belong to the domain — a value that also vanishes the denominator is not a zero.
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