Rút gọn B=\(\frac{a}{a+3}+\frac{2a-1}{a-3}-\frac{2a^2-a-3}{a^2-9}\)
Rút gọn A=\(\left(\frac{a^3-3}{a^2-2a-3}-\frac{2a-6}{a+1}+\frac{a+3}{5-a}\right):\frac{a^2+8}{a^2-1}\)
Cho \(M=\frac{1}{a^2-2a+1}-\left(\frac{a}{a^2-1}-\frac{1}{a^3-a}\right):\frac{a^2-2a+1}{a+a^3}\). Hãy rút gọn M.
\(\text{GIẢI :}\)
ĐKXĐ : \(a\ne\pm1\).
\(M=\frac{1}{a^2-2a+1}-\left(\frac{a}{a^2-1}-\frac{1}{a^3-a}\right):\frac{a^2-2a+1}{a+a^3}\)
\(=\frac{1}{a^2-2a+1}-\left(\frac{a}{a^2-1}-\frac{1}{a\left(a^2-1\right)}\right):\frac{a^2-2a+1}{a+a^3}\)
\(=\frac{1}{a^2-2a+1}-\left(\frac{a^2}{a\left(a^2-1\right)}-\frac{1}{a\left(a^2-1\right)}\right):\frac{a^2-2a+1}{a+a^3}\)
\(=\frac{1}{a^2-2a+1}-\frac{a^2-1}{a\left(a^2-1\right)}:\frac{\left(a-1\right)^2}{a\left(1+a^2\right)}\)
\(=\frac{1}{a^2-2a+1}-\frac{\left(a-1\right)^2}{a\left(a^2-1\right)}\cdot\frac{a\left(a^2+1\right)}{1+a^2}\)
\(=\frac{1}{a^2-2a+1}-\frac{\left(a-1\right)^2}{1+a^2}=\frac{-a^2}{\left(a-1\right)^2}\).
Rút gọn A = \(\left[\frac{\left(a-1\right)^2}{\left(a-1\right)^2+3a}+\frac{2a^2-4a-1}{a^3-1}+\frac{1}{a+1}\right]:\frac{2a}{3}\)
\(=\left[\dfrac{\left(a-1\right)^2}{a^2+a+1}+\dfrac{2a^2-4a-1}{\left(a-1\right)\left(a^2+a+1\right)}+\dfrac{1}{a-1}\right]:\dfrac{2a}{3}\)
\(=\dfrac{a^3-3a^2+3a-1+2a^2-4a-1+a^2+a+1}{\left(a-1\right)\left(a^2+a+1\right)}\cdot\dfrac{3}{2a}\)
\(=\dfrac{a^3-1}{\left(a-1\right)\left(a^2+a+1\right)}\cdot\dfrac{3}{2a}=\dfrac{3}{2a}\)
CHO BIỂU THỨC:
M = \(\left[\frac{3\left(a+2\right)}{a^3+a^2+a+1}+\frac{2a^2-a-10}{a^3-a^2+a-1}\right]:\left[\frac{5}{a^2+1}+\frac{3}{2a+2}-\frac{3}{2a-2}\right]\)
a) rút gọn M
b) nếu a = 2 thì M = ?
c) nếu M = 0 thì a = ?
Rút gọn biểu thức sau : \(R=\left(\frac{a-2}{2a-2}-\frac{3}{2-2a}-\frac{a^2+2a+3}{2a+2}\right).\left(1-\frac{a-3}{a+1}\right)\)
Bài này mình ra kết quả không gọn lắm, nên muốn tham khảo đáp số của mọi người ạ!
Rút gọn \(A=\frac{a^3+2a^2-1}{a^3+2a^2+2a+1}\)
cho biểu thức :\(\left(\frac{2a-a^2}{2a^2+8}-\frac{2a^2}{a^3-2a^2+4a-8}\right)\left(\frac{2}{a^2}+\frac{1-a}{a}\right)\)
a) Rút gọn A
b) Tìm các giá trị a nguyên để A nguyên
Rút gọn : \(\frac{a}{2}.\left(\sqrt[3]{a^2b}+\frac{b}{a^2}.\sqrt{\frac{15a}{b^2}}-\frac{4a}{5b}\sqrt[3]{\frac{b}{2a^2}}\right):\frac{2a^3}{15b^2}.\sqrt{\frac{5a^2}{2b}}\)
rút gọn
\(\frac{a^3+2a^2-1}{a^3+2a^2+2a+1}\)