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9.1: Simplifique as expressões racionais

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    170319

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    Definição: Expressão racional

    Uma expressão racional é escrita como um quociente de polinômios

    \[\dfrac{P(x)}{Q(x)} \nonumber \]

    onde\(P(x)\) e\(Q(x)\) são polinômios em uma variável\(x\).

    Para simplificar uma expressão racional, fatore o numerador e o denominador e remova fatores comuns do numerador e do denominador. Uma expressão racional simplificada tem apenas uma divisão e um único numerador e denominador. Se as expressões não puderem ser fatoradas, a expressão racional não poderá ser simplificada.

    Exemplo Template:index

    Simplifique as expressões racionais:

    1. \(\dfrac{x^2 + 2x − 3}{x^2 + 4x + 3}\)
    2. \(\dfrac{(x^2 + 1)^2 (−2) + (2x)(2)(x^2 + 1)(2x)}{(x^2 + 1)^4}\)
    3. \(\dfrac{(x^2 + 1) \frac{1}{2} (x^{−\frac{1}{2}}) − (2x)(x^{\frac{1}{2}})}{(x^2 + 1)^2}\)

    Solução

    1. \(\begin{array} &&\dfrac{x^2 + 2x − 3}{x^2 + 4x + 3} &\text{Example problem} \\ &\dfrac{(x + 3)(x − 1)}{(x + 3)(x + 1)} &\text{Factor both numerator and denominator.} \\ &\dfrac{\cancel{(x + 3)}(x − 1)}{\cancel{(x + 3)}(x + 1)} &\text{Remove common factors, because \(\dfrac{x + 3}{x + 3} = 1\)}\\ &\ dfrac {x − 1} {x + 1} &\ text {Resposta final}\ end {array}\)
    1. \(\begin{array} &&\dfrac{(x^2 + 1)^2 (−2) + (2x)(2)(x^2 + 1)(2x)}{(x^2 + 1)^4} &\text{Example problem} \\ &\dfrac{2(x^2 + 1)[(x^2 + 1)(−1) + (2x)(2x)]}{(x^2 + 1)^4} &\text{Factor out 2(x^2 + 1)} \\ &\dfrac{2 \cancel{(x^2 + 1)}[(x^2 + 1)(−1) + (2x)(2x)]}{\cancel{(x^2+1)}(x^2 + 1)^3} &\text{Remove common factors, because \(\dfrac{x^2 + 1}{x^2 + 1} = 1\)}\\ &\ dfrac {2 [−x^2 − 1 + 4x^2]} {(x^2 + 1) ^3} &\ text {Simplifique multiplicando e combinando termos semelhantes}\\ &\ dfrac {2 (3x^2 − 1)} {(x^2 + 1) ^3} &\ text {Resposta final}\ end {array}\)
    1. \(\begin{array} &&\dfrac{(x^2 + 1) \frac{1}{2} (x^{−\frac{1}{2}}) − (2x)(x^{\frac{1}{2}})}{(x^2 + 1)^2} &\text{Example problem} \\ &\dfrac{\frac{(x^2+1)}{2x^{\frac{1}{2}}} − (2x)(x^{ \frac{1}{2} })}{(x^2 + 1)^2} &\text{Work with the negative exponent in the first term of the numerator by moving the factor to the denominator of the first term, next to the \(2\).}\\ &\ dfrac {(x^2 + 1) − (2x) (x^ {\ frac {1} {2}}) 2 (x^ {\ frac {1} {2}})} {\ dfrac {2x^ {\ frac {1} {2}}} {(x^2 + 1) ^2}} &\ text {denominador comum}\\ &\ dfrac {x^2 + 1 − 4x^2} {(2x^ {\ frac {1} {2}}) (x^2 + 1) ^2} &\ text {Simplifique multiplicando e combinando termos semelhantes}\\ &\ dfrac {−3x^2 + 1} {(2x^ {\ frac {1} {2}}) (x^2 + 1) ^2} &\ text {Resposta final}\ end {array}\)
    Exercício Template:index

    Simplifique as expressões racionais:

    1. \(\dfrac{2x^2 + 3x − 2}{2x^2 + 5x − 3}\)
    2. \(\dfrac{(t^2 + 4)(2t − 4) − (t^2 − 4t + 4)(2t)}{(t^2 + 4)^2}\)
    3. \(\dfrac{(2)(x − 4)(x^2 + 4x + 4)}{(x + 2)(x^2 − 16)}\)
    4. \(\dfrac{12x^2 + 19x − 21}{12x^2 + 38x − 40}\)