RÚT GỌN C=\(\left(\frac{1+a^3}{1+a}-a\right).\left(\frac{2a^2+4}{a^3-8}-\frac{a}{a^2+2a+4}\right)\)
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\(=\left[\dfrac{\left(a-1\right)^2}{a^2+a+1}+\dfrac{2a^2-4a-1}{\left(a-1\right)\left(a^2+a+1\right)}+\dfrac{1}{a-1}\right]:\dfrac{2a}{3}\)
\(=\dfrac{a^3-3a^2+3a-1+2a^2-4a-1+a^2+a+1}{\left(a-1\right)\left(a^2+a+1\right)}\cdot\dfrac{3}{2a}\)
\(=\dfrac{a^3-1}{\left(a-1\right)\left(a^2+a+1\right)}\cdot\dfrac{3}{2a}=\dfrac{3}{2a}\)
\(M=\left(1+\frac{a}{a^2+1}\right):\left(\frac{1}{a-1}-\frac{2a}{a^3-a^2+a-1}\right)\)
\(=\left(\frac{a^2+1}{a^2+1}+\frac{a}{a^2+1}\right):\left(\frac{a^2+1}{\left(a-1\right)\left(a^2+1\right)}-\frac{2a}{a^2\left(a-1\right)+\left(a-1\right)}\right)\)
\(=\frac{a^2+a+1}{a^2+1}:\left(\frac{a^2+1}{\left(a-1\right)\left(a^2+1\right)}-\frac{2a}{\left(a^2+1\right)\left(a-1\right)}\right)\)
\(=\frac{a^2+a+1}{a^2+1}:\frac{a-1}{a^2+1}=\frac{a^2+a+1}{a-1}\)
\(C=\left(\frac{1+a^3}{1+a}-a\right)\left(\frac{2a^2+4}{a^3-8}-\frac{a}{a^2+2a+4}\right)\)
\(=\left(\frac{\left(a+1\right)\left(a^2-a+1\right)}{1-a}-\frac{\left(1-a\right)a}{1-a}\right)\left(\frac{2a^4}{\left(a-2\right)\left(a^2+2a+4\right)}-\frac{a}{a^2+2a+4}\right)\)
\(=\left(\frac{a^3+1-a+a^2}{1-a}\right)\left(\frac{2a^4}{\left(a-2\right)\left(a^2+2a+4\right)}-\frac{a\left(a-2\right)}{\left(a-2\right)\left(a^2+2a+4\right)}\right)\)
\(=\left(\frac{a^3+1-a+a^2}{1-a}\right)\left(\frac{2a^4-a^2+2a}{\left(a-2\right)\left(a^2-2a+4\right)}\right)\)
\(=\left(\frac{a^3+1-a+a^2}{-\left(a-1\right)}\right)\left(\frac{2a\left(a^3-1\right)}{\left(a-2\right)\left(a^2-2a+4\right)}\right)\)
tình nốt nhé, thấy sai sai ở đâu á, kiểm tra lại zùm mk