以下為您提供一些人教版初二數(shù)學(xué)分式計(jì)算題及答案:
1. 先化簡,再求值:1/(x + 1) - 1/x(x^2 - 1),其中 x = 2 + 1。
解:原式 = 1/(x + 1) - (x + 1)/(x + 1)(x - 1) = -x/(x + 1)(x - 1) = -x/(x^2 - 1),當(dāng) x = 2 + 1 時(shí),原式 = - (2 + 1)/(2^2 - 1) = - (2 + 1)/3 = - 2/3 - 1/3 = - 1 - 2/3 = - 5/3。
2. 先化簡再求值:1 - 1/(x + 2)(x^2 - 1)/(x + 2),其中 x = 2。
解:原式 = (x + 2)/(x + 2) - 1/(x + 2)(x + 2)(x - 1)/(x + 2) = (x + 1)/(x + 2)(x + 2)(x - 1)/(x + 2) = 1/(x - 1),當(dāng) x = 2 時(shí),原式 = 1/(2 - 1) = 1。
3. 先化簡,再求值:1 - 3/(x + 2)(x^2 - 2x + 1)/(x^2 - 4),其中 x = 1/2。
解:1 - 3/(x + 2)(x - 1)^2/((x + 2)(x - 2)) = (x + 2)/(x + 2) - 3(x - 1)^2/((x + 2)(x - 2)) = (x - 1)(x - 2)/(x + 2)(x - 2) = (x - 1)/(x + 2),當(dāng) x = 1/2 時(shí),原式 = (1/2 - 1)/(1/2 + 2) = - 1/5
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